Doug,

I have not noticed the same thing with alu masts, quite the opposite actually. Without downhaul we might have to pull the boom over to windward forcefully to make the battens pop over. Sometimes when going downwind in light conditions we have cranked on the downhaul to make the battens pop over instead of yanking on the boom.

Wouter, mainsheet and downhaul both shapes the main and works together of course. What I am pointing out is that you dont necessarily damage the main by pulling on the downhaul without mainsheet. Turning downwind in a blow on the other hand.. Chasing wraiths? Where did the scientific, argumentative, Wouter go <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />