An interesting debate regarding smaller sails.
Our small mainsail is only about 1m2 less in area than our full size one, all the area is taken out of the head, it is cut slightly flatter than our full size main, and is matched to the luff curve of the mast. It is not the only change we make when it's windy, additionally we rake the rig back by 2-3", this helps with the balance of the boat and also opens the leech of the jib depowering that as well, we also ease the uppers (from max power setting) to allow the mast to work a bit more upwind, but not too much for the mast to go over the front downwind. The advantages of the small main are less drag upwind, slightly easier at low speed manoeuvres (start, kite hosts/drops ans tacks) and finally it's quicker to right from a capsize. I don't think its make much difference on the bear away as the t-foil does all the work for us. Note we won the light wind race at the inlands at QM with the small mainsail against a majority of full size sails.
It certainly has saved some wear and tear on the full size main which has now allowed us to go to a lighter cloth saving weight and some money.
There is no reason that the heavier sailors couldn't develop a more powerful rig to increase their light wind performance, stiffer masts, fuller sails, more upright rig, put this on a hull that carries weight a bit better and I would imagine that any performance deficit could be greatly narrowed.