I can't really discuss 2 up but when 1 up I sheet as hard as I can when I can. This usually means until I physically can't pull any more. The sail is as tight as it can go, if I am then constantly bearing up in the gusts or having to ease the main then I pull some more downhaul on still trying to keep maximum pressure on the mainsheet. This technique is only used in medium wind conditions and I all ways try to remember to ease to the downhaul just prior to rounding the windward mark just to save the sail from over stretching the luff. However, I do forget occasionally ;-(