Back to sailing: On the question of having the sail lay over the spreaders I don't mind too much. I can see that would be bad for long cruising passages. But on a half hour race leg, I don't think it's so bad. I used to do it all the time on the H356, my Mark 25, my friend's Tartan 33, the J32C, j105 and J109. Hopefully there are some spreader patches but you can have the main sail laying over swept back spreaders without damage. I've tried tacking down wind in club races and the legs just aren't long enough for this to pay off.
The second point is about Thinwater's picture. If you enlarge it, I think you see the top leeward tell tails on the forward part of the sail are streaming towards the middle. And maybe even the aft tell tails are streaming. This is visual evidence of what Jackdaw posted. The middle, I can't see so well at magnification and the lowers aren't in the picture. So as to the question of how much depth in the sail, I would suggest looking at those tell tails. If you are getting flow, you are getting lift. You'll never see it in the bunt tell tails (As shown on Thinwater's pic), but you might on the fore and aft. If you can't get flow on those, I'd just go for barn door mode. In higher winds, there will be just stall vortices, I think. But you won't care because you'll be doing hull speed.
