Does anyone use the dyneema sk99 or max for standing rigging?
If so any tips or warnings?

Simon, it'll shrink in the sun. Only a bit but you'll lose your settings. Not a good idea. The B14 2 - 1 main halyards shrink up to 30 cm during their life which starts life at 7.3 m. of rope = up to 4%

Hi Mark,
i believed that the shrinkage is most likely cause by being inside a black mast during the summer and under no load. The specs of the M-rig (and even the D12max) show zero creep and as far as the geeks at marlow tell me as long as some light load is maintained on the rig then it shouldn't shrink. Most of the shrinkage is as you rightly say caused be temperature but a shroud even on a 40degree day won't get hot enough. A B14 halyard inside a black mast.....
Might make a set and see how they fair, it is 50% lighter at least, so maybe worth testing..
Was interested to see if anyone in the fleet had changed over, as the rig is easy(ish) to fine tune.

It shouldn’t shrink but it does!

Try using DM 20

It’s designed for making shrouds from.

Simon, Jimmy Green Marine have a deal on for M-Rig Max (DM 20)

Hi Mark,
i have the string, i guess marlow are keen for dinghy guys to have a go! 

One consideration with rope is how it will be affected by the Spreader Bracket and if there will need to be a change to prevent chafe there.

You should probably look to use some very small ferrules at the spreader ends unless you fancy fabricating your own spreader tips.

In the moth class a number of guys are using old rivets drilled out to give a smooth surface, then just insert into a standard spreader fitting.