Hey there,
Best idea is demo what your looking at!
The Sub vector i believe was built for bigger guys up to about 105kg, best person to talk to about that is Simon from Newcastle Sup he is the Guru on the C4 boards. I am sure C4 have other boards that would also suit.
Naish 9'3 is a great board a mate Matty Mathews is about 90kg and rips on this board. It from what I have seen is more unstable as it has a tighter pulled tail. PM the dogman he is the guru on the 9'3.
Piros and Laceys lane have ridden the Gerrys and by all accounts they too are very fine boards. Drop them a PM they will help no end.
At 77kg you might like to think about:
The PSH 9'3 Ripper less rocker more stable HP board.
Andrew Allen Balmoral Boards is the Guru on the PSH Range
Naish 8'10 Alicat surfs this board like a weapon,
DC 8'10 Session is about 85kgs and says this is very stable and he rips,
LSD 9'2 Steve was killing it on this board and he would be mid 80s too i think, slap me if I got that wrong Steve laughs.
Hope this helps
Phill

