Many single cams will come with a high letoff, over 75% and have an option for a 65% letoff. Of the single cams that I' ve tried with a 65% optional cam, it seems they acheive the lower letoff simply by cutting the valley out of the draw cycle. I find it rather uncomfortable. Creep even a millimeter, and the cam grabs hold and wants to take off.

Does anyone know of a company who offers the optional 65% letoff cam that gives you a true valley before the wall?