M_Boats: M15 heel angle?

I had a nice sail on lake Pleasant AZ last Sunday. The winds were variable as usual but I was playing with the angle of heel and the GPS (getting ready to win the Havasu Montgomery race). The M15 seems to sail faster in 6 - 10 kt winds when it is kept reasonably flat. At lower winds it seems to like a little more heel. What do you other M15 sailors think? How do alter the hull trim for different wind conditions to maximize your speed ( velocity made good)? Thanks Doug