Can any offer me some advice, I'm getting creases on the main sail from the clew up to the spreaders and hounds, and the more kicker I pull on the more creases we get, how do we get rid of them I'm sure they're not fast! We have a carbon mast if that makes a difference, although I'm sure I could manage them with an ali mast as well.

I asked the same question with my Goachers on Carbon rig and was told they were 'Speed' creases

from the (excellent) national 12 tuning guide:

"Remember that in most conditions you should see slight wrinkles running perpendicular to the mast at the luff. If you tension the Cunningham and remove these creases you will almost certainly have compromised your sail shape and power."

My understanding is, creases from the clew is an indication of excessive mast bend increasing kicker will bend mast more. Suggest using more lowers.

The "speed creases" are just at the luff running horizontally.  These creases from the clew are from the mast bending more than the sail is cut for.  To reduce bend, more lowers, spreaders forward, don't overdo the kicker. Which mast?  I've never managed to get them on my Superspar which is very stiff low down.

Its a Chipstow, more lowers doesn't seem to help, perhaps I should look at adjusting the spreaders forwards!

hope I can help, there are many things that can cause creases from the luff of the sail, the main cause is over bending the mast, or the sail not fitting the mast bend correctly can be due to the sails age or cut, if you can post a picture of the sail or email a shot I can advise a solution

Dave thankyou I'll try and get a picture at the weekend