Clocked 60km/h with my 7.8 OD R8 with 36cm fin yesterday, a day before a friend pushed his iS107 with R8 7.8 to 65km/h with an 38cm cfins. the conditions where gentle chop (max 30cm) on lake biwa, still uncomparable to the 42 knots that Twan did... we need to add 12kg quickly
You guys should try a 35cm Sonntag SLR on your 107's,especially with a 7m. It has a really nice feel to it,very slippery and super smooth in the chop.
Its shaped and feels very much like the old Techtronic Falcon. For some reason it has a lot of lateral stability despite its small area and it rarely if ever feels like it wants to let go. I have used it on my 97 Sonic as well but it actually feels too big and powerful.
7.0m felt best with the 107 when I owned my 2015 107,with bigger sails the board felt like it had too much downforce on it and as a result it sat lower in the water.
I now use my 35 cm Sonntag SLR on my 71cm wide Manta with my 7m and it feels awesome,especially in the gusts. With a 38cm Carbon Volt and a 7m I can feel the extra length creating a lot more drag.