I have just bought a Winder Mk5, but having not raced a Merlin for about 5 years I am out of touch. I have some upgrades in mind, but advice on the following points would help me spend wisely. 
 
The list includes:
 
1) Moving the jib tack forward. What are the benefits and any drawbacks?
 
2) increasing the size of the spinnaker chute. Does this require a measurement check to be legal?
 
3) Replacing the Paragon high modulus mast with a skinny mast. How much difference does this make to performance? 1 Bad tack per beat or greater? 
 
4) Replacing the standard centreboard with a JT or similar, is there any benefit? 
 
I would welcome some help and guidance, before committing to anything expensive.
 
Many thanks in anticipation
Steve 

 Hi Steve,
 
In terms of the Jib Tack, if you move it forwards it appears to improve the performance, but may be more in the mind.
 
If you do move that you would be better with a larger chute, which doesn't mean you need to be re-measured, unless you want to check if the boat needs the correctors changing, as the smaller chute will cause issues on the hoist/drop as the Spinnaker pulls on the jib if the kite is at all on the other side.
 
In terms of changing the Mast or Centreboard I would get familiar with the boats again before moving onto those changes whilst you get back in touch, as the boat should be competitive as it is.

Thanks Stuart for the advice, it is very useful. I also have a Scorpion and so I am used to the jib tacked on the bow, and I have just had the chute enlarged to make launching and recovery of the spinnaker easier, especially now they have significant stiffening in the clews. 
I will test the stiffness of the current centreboard and that may be something for the future, before the expense of a mast.  I am not sure that 5 mm less diameter will make a big difference. However,  the mast is a Paragon hi-modulus mast, which I believe is a stiff mast. That could be a problem as we will sail with around 135 kg crew weight, but perhaps you could advice me on that point.
I will probably change to lazy guys for the Spinnaker, and the pole launching system is very different to the one I am used to. It seems to have too many bits of elastic and cord, including a Snodger, which seems unnecessary if I rig the fly-away poles the same way as on my other boat.
 
If you or anyone else have any thoughts on the above I would be most grateful. 
 

   Not wanting to be accused of self promotion, but this might give you some food for thought on poles. 
 If this link does not work have a look for rockatross on FB and go to video's you will find the video of pole set up there. Hope that helps you.

 Hi Steve,
 
The poles have two different types of systems for getting the ring to the end.  
 
It sounds like you have the system where the pole downhaul also takes the ring to the outer end of the pole, thus the snodger is still required to get the ring right to the end.  The elastic is required for a number of reasons, based on the launcher you have.  The Merlins have found that the EZI-Launcher and similar variants have a tendancy to not release the end when the line is freed, thus there is some elastic to pull it down.  The crew position is also slightly different, so there is often elastic to keep the inboard end close to the boom when it is flying back to help prevent the crew finding the end in their face!
 
The other system is often referred to as the 'Musketeer' system where the ring is pulled to the end of the pole by the launch line and has a 1:2 purchase inside the pole to shorten the amount of line that is pulled by the crew on the launch.  For this system you don't need the snodger as much, as it then becomes a simple pole downhaul.
 
If you look at the Videos that Rockatross have on Facebook and I have also posted a few of systems on the Merlin Rocket Revival Group on Facebook that may help, including the Pump Action Spinny Halyard systems.

pastingpastingI’ve only been out three times since doing a refit on my boat, and always in 15 knots plus, my aim was to get option to adjust more inboard/outboard positioning for the jib sheet rather than just the standard fore/aft adjustment.
 
All the smart people I spoke to at North Sails UK said that the Jib slot is more important than a stem tack position and having a larger jib/mainsail ratio, so far they seem to be right.
 
Having sailed stem tacked jib boats and my own before and after X/Y surgery she sails the same as the stem tacked boats. Easier to keep in the groove up wind. 
 
Don’t rush in to bow tack mods maybe consider that other factors are also important. 
 
Now just got to get rid of the Serious amount of rust on the nut at the end of tiller... 
 
We are planing to do lots of training at LTSC this autumn. This week I have been discussing with David Lenz about getting out on as many Saturdays as possible to try and treat that rust problem quickly. If people want to come and play, let me know...! Always keen to have friends come join in.
 
As said above best practice is to get out on the water and sail the boat and figure out what modifications would suit you best. Budget and plan them out. I have sailed my boat for a few years before doing an overhaul.
 
My Winter Mods were:- 
 
X/Y jib sheeting
Re-Grip with SeaDek
New Foils from JT
Adjustable toestraps front and back
new JT Locking Traveller 
Moved Jib and Kite sheets forward and inboard
Lazy guys but with a cascade rather than 3:1 purchase 
 
All seem beneficial but need to put in a lot of time on the water to really make a difference
 
 

Also Steve I am pretty sure that the Paragon Rigs are skinny and Hi-mod Carbon. They are around 45mm diameter sections?
 
There are lots of very good masts on the market. 
 
Selden
SuperSpars
Paragon
CST
Jon Turner
Ceilidh 
 
Great to have so many options for masts. Pretty sure if you have bought Smokey it was an ex-P&B works boat and is pretty well set up and equipped with good gear. Very well looked after by the previous owner too.
 
 The only thing I wasn’t sure about on her was the weird P&B Spiro Pole Launcher It has but crewed in it once and it worked really well.
 
Really wouldn’t change much until you’ve sailed her a bit, she has always been a fast boat. 
 
 
 

Thanks Stuart, John and Gareth, this is all very helpful and yes it is Smokey (formerly The Dark Side). 
 
I have decided to move the Jib tack forward, and extend the Chute mouth. I have building works at home for 12 weeks so have got a reputable boatbuilder to do this job. I will also need to source sails to go with the new set up. I am interested in changing to a bigger Jib/smaller Main, so a chat with a few sail makers is called for, plus shorter boom and some remeasuring. 
 
The pole flyaway system is P&Bs own version, with large sheaves and replaceable rollers. It is different to the Spiro,  but I am hopeful I can make it work with modifications based on all the help you good people have provided. I like the idea of a cascade system for the lazy guys and will have to look at ways of achieving X-Y sheeting for the Jib.
 
The Paragon Mast is 45mm diameter, so it will stay, as I don't have money to burn!  I will have to play with the spreaders if it seems a little stiff for our crew weight.
 
Unfortunately, sailing her is also not an option at present, as my wife/crew is incapacitated for 3 months. I am relying on all the things that bugged me with the two Mk IVs I've sailed, and your videos to personalise the various controls and sheeting arrangements. I will no doubt have to revisit some mods, until I get them right.
 
 
 

For the x/y I looked at the system Simon Potts has From Jon turner in khaleesi and found that very easy to install. Likewise Dave Winders jib bar system would be easy to install too.