Its hard to find info on these. Looking at grabbing one of these now while they are on special. I mostly use my 14m New kite at the moment and Im really enjoying it.
Comfortable size for me but it's flogged. I'll need a new kite for this winter windy season.

What is the best size for me 100kg on a 145 Twin tip in rough ocean. Usually no real waves.
Generally dont get much over 25 knots.
Im told the 12m express has about the same power as my 14m os

Anyone know more?

Go for a 15m, the 12.5m is for a lighter weight rider.

If you're a big fella there is no point in stuffing around with small kites in marginal winds.