That's what I needed to know.
Since it sounds like your still kind of learning the ropes, the Forces might work for you, it might be nice to have a little forgiveness, and it is a good binding. 25.8 is kind of boarderline to a wide board but most marketed wide boards in my experience are over 26, but that is irrelevant here. For your style of riding and your size, if you buy the Forces, get the M/L.
However, you brought up a good point with the flex rating, if you want more response, I would definitely look for a stiffer binding. If you want suggestions, Rome Targa, Ride El Hefe, Flow NXT(maybe, haven't tested myself), Flux DMCC(another I have not tested but heard good things about), I would also say stay away from Burton as their overall quality is uneven from year to year, and 4 people I know have had broken toe straps.
Anyone else here have suggestions?
When I was in the Army I knew a man who had 3 rules about sex, one of them was "quantity not quality". I really regret not asking him what 200 pound twins would classify as.