I have the 82 polakow twin from surfladle shoreham and like it, :-)
heres what I reken, I set the mast foot quite forward and the fins back a little, straps forward too, it seams better when you turn off your front foot more, the board turns better the faster you go, it does have a certain rate of turn not quite as tighter turn as my Mistral twin but when turning on your back side my god does it grip...
one thing I really notice is when dropping in on waves it will not slide off the face of the wave until you turn, only board I've sailed to do this I guess thats the concave in the rails
I like it for 5.0 powered sailing and when the wind picks up it seems to really settle in, I think it will sail well with a bigger sail probably really well with a 5.8 (I've not used any bigger than 5.0). 4.5 is def the smallest sail I'd use then change down board I'm 12.5 stone
jumping is pretty good for a twin with the rocker trough the tail you can drive the speed quite fast for jumping, really easy to control and steer in the air, I've very nearlly landed some more backies on this board
I hope this is some sort of help,