not asking for too much but we are all different and there may not be one single answer for you
the waves you surf will also be a big influence on the style of board
I'm not familliar with SA but tell us which breaks and what size waves you are aiming at
... quad or tri and what part of the wave do you like to hang in or on
I'm not as heavy as you but here are my boards
http://www.diyfactory.com/surf/Kev01.htm
the Neil Like Freak ... third board down was owned by a fellow around your weight
he surfs the Vic west coast
mostly point and reef breaks
and finds a board this size floats him fine
The two newer boards where made recently by Dave P and I wanted to try more float and to experiment with Fin arrangements
The newest board at the top is very floaty ... I've taken to calling it the FatBoy
in conditions that require many duck dives it is probably too floaty and in choppy conditions it can be hard to sit on
I haven't yet had it in the small conditions it was made for
so I can't say for sure that it is too fat
The flat rocker is very fast and can make for a difficult turn ... I like it as a Quad
the Second board is a very good all-rounder and I seem to like it as a Tri
Dr Red likes to talk a little about volume ... in litres
he likes 30 ... ish and seem to wants to get even smaller
and I seem to like high 30 and perhaps over 40 litres
he likes narrow 22 to 23
I seem to like 23 to 24
very broad starting point
6' to 6'2"
22 3/4 through to 24 wide
2 1/2" for thin and I think more like 2 3/4" through to 3 inch thick
IF you are ever in Victoria ... you are welcome to try any of them