With the same rig?..... no, I don't think you will find that a formula board (even the higher volume F-186) is going to lower your planing threshold by 2 knots.
Formula boards are 100.5 cm wide, same as your Start.
The extra volume is what's making alot of the additional board weight, and at your size that extra volume is probably a good thing.
Work on your skills to get the most from your Start.
If you can find an F-186 (172 liters volume) give it a try, but I don't think you'll get anything like a 2 knot drop in planing threshold windspeed.
With a different rig (larger).... maybe, but you already have an 11.0 m2 Retro and larger sails don't have alot of low end, so you are pretty much "maxed out" on rig size.
Are you rigging your big Retro for max. early planing....i.e. batten above the boom pulled back 1/2 the mast diameter and tangent to the lee side of the mast?
Do you have an adjustable outhaul so you can really "fatten up" your big Retro for max. light wind "grunt".
Where do you have your footstraps.... all the way back and outboard?
If yes to all of the above, I think you need to work on better pumping skills as that's about the only thing that's not already optimized.
If you have a chance to borrow or rent a formula board, give it a try, but I'll be surprised if you come back and tell me you were planing in less wind.
Be really "active" in your pumping, that's about the only thing that will lower your planing threshold.
A formula board might be better upwind (but not an marginal planing windspeeds) and might be faster on the top end, as well as way off the wind, but it's not going to plane for a big guy a whole lot sooner.
Have you tried a 70 cm fin in your Start to see how much that improves/diminishes your planing threshold? Sometimes the super big fins get you going slightly sooner, but soon become a liability in terms of top end speed.
Last edited by Roger; 10th October 2008 at 09:41 AM.