Big Ed proved us wrong with hitting a 76,79 km/h 2 sec topspeed with an 2011 iSonic 117w (80 cm!) and a 10 sec run of 73,34 km/h!
www.gps-speedsurfing.com/default.aspx?mnu=user&val=86826&uid=1433
Size matters for going fast. Height and weight is an advantage. As Matt said, you can only strap so much weight on... and the big guys can (and do) strap even more on... and have an even bigger advantage. As I've said before, if you are getting beaten by a shorter, lighter dude in speed, then you aren't making the most of the conditions.
Bjoern and AA were always adding weight on the speed tour. I dont think they do this just for fun.
Its good to see some huge guys going fast on big boards. I dont see regular size guys pushing boards this big to those speeds though. I mean even if this board is big for normal people, its still a total sinker for this guy.
The leverage moment only depends on how far outboard the centre of gravity of the rider is. The harness and boom positions are internal forces which, unless they restrict how far outboard you can get your c of g only really affect comfort and control.
The leverage moment is of course balanced by the moment of the sail. You can hold onto a more powerful sail if the lift is centred lower down.
The width of the board is important because if you can sail with the board railed to leeward, the fulcrum shifts off axis. Thus you have more moment available to hold down sails. You need to select the correct size fin to be able to let the board rail to leeward comfortably. If the fin is too short you'll need very strong ankles to cope with the internal forces required to rail the board leeward.
Formula boards railed to leeward can get the sailors weight a long way from the fulcrum and can take large sails.
The effect is most pronounced and easier to see in a catamaran which is sailed on the leeward hull giving a sailor a lot of leverage to hold big sails.
Here's an idea I had a while ago on an asymmetric speed board which combines the width to carry a larger sail with the narrowness to not get bounced around too much in chop. Why stop at asymmetric fins?
do you have read this?http://www.star-board.com/2012/news_events/read.php?post_name=77kmh-on-an-isonic-117-wide
It's not only the weight, it has to be your style to surf with large sails en boards, I surf allready more than 20 years, when I was 18 years old (80 KG weight) I allready surfed more then 1m2 larger then everybody else :)
now a days the sails and boards are more suited for overpowered speedsurfing.