Last night I raced in 15 knots with the #1 (we race non-spin, so almost always fly the #1)and 4 crew total. Upwind we were all on the rail and I was steering and playing the main to keep the boat flat - so the main at times was flapping. We did well. At the bar a J/24 sailor said we should have dropped the traveler all the way and sheeted the main flat. Opinions?
Depends which is easier on your boat, playing the traveler or the mainsheet. Upwind overpowered and underweight, flatten the main using tight outhaul, vang, cunningham and backstay. Personally I would sheet in and and play the traveler first to control the heel. If the traveler at or near the bottom of track is not enough, 'vang sheet' by playing the mainsheet. Once you are in that mode you'll probably want to pull the traveler back up to the middle so you can use the cleat more easily. Be careful to avoid inverting the mainsail with too much backstay. You can tell when this happens by the windward bubble in the center of the sail. After all of the above, if you are still overpowered and don't want to change headsails, ease the jib sheet and move the car aft to open up the top of the sail. Much easier to feather in the puffs with a #3 than a #1 which can lead to the dreaded 'auto-tack'.
I like to get the main board flat when breeze is up or crew is light (or both)-best achieved by high rig tune (at 15 knots with light crew I would be between 39 and 40 on the Loos on inners and outers). Mainsheet tight and leave it that way, play the traveler aggressively, play the backstay in big puffs to drop the top of the sail off. If the main is sufficiently flattened, it should only bubble a bit when the traveler is dropped and will rarely flog.
In flat water/solid breeze with light crew, (if you have enough manpower) have you ever tried going with the three upwind and changing to the 1 for the downwind?