Good morning, Joe,

You might get more responses posting on the iWindsurf Forum.

Can't comment about the OFO vs. fin length. In the old days, the OFO measurement wasn't part of the board specs.

Sadly, I started sailing in the era your question concerns and can recall a number of US box failures as fins got bigger, so suggest that you go no bigger than a fin length of about 32cm (the biggest offered on 1992 Bic boards). The boxes just weren't designed for big sideways forces generated by big fins and that's why the Tuttle, Power and Trim boxes were invented. By the way, if you do go big and you hear a CRACK whilst sailing and the board suddenly goes sideways, you'll instantly know that you've gone too big.

Re fin position in the box. Those race boards were made for going (relatively) fast in a straight line and only needed to complete (perhaps) 8 gybes before the race was over. Is there really a need to get excited about fin position on a board 3.5m long and if there is, why don't you alter the fin position (full forward vs full aft) and try to feel the difference?

Hope this helps.

okay then, is it worth converting the US box to a power box ??
as seen here

in the video clive just jams it in , locks it in place with the old mould and then glues it

i guess the idea is - am i ready to take a chance or just enjoy the board as is !!
and forget bigger than 32 cm fins

the board planes up early and feels fast - big heavy speedster like the cars of that time :-)

also heard or read, with US box if you move fin forward, you get more steering
and back for "control"
is this also true ??

With a surfboard the general rule is move the fin forward for quicker turning and further back for stability and speed down the line, I would think you would want that fin as far back as possible.

i wouldn't worry about swapping out the finbox unless you can't find fins. i'm not sure if your board has one of those exotic boxes some long boards had.

just stick a narrow chord 30cm fin in for when the winds up and the wide chord one when the winds not up. the narrower fin will help your turns but to be honest the stiffness you describe is more about the rocker/rail shape.

i'd just get the narrow chord fin and be done with it or buy a different board. a lot of guys, myself included used to use finworks fins in our raceboards. they were half decent fins.

maybe try something like that.

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M-m-m-m-m, Finworks fins