I use Ian Dixon for foils. Sorry lost my mobile this week so don't have his number. His email is info@dixonboats.com Not sure who everyone else uses
Spars some of the guys are using CST, some C-Tech, and Goldspar for the aluminium (not many of them left)
Haven't seen any double pole systems. If you get onto the international website they have a copy of the rules and that should tell you.
Hope to see you out on the water.
Cheers
John