I can use 85 head pretty effectively, but because of my short draw length I use shorter arrows. I shoot like 25-26 inch arrows with feathers, so FOC is never much of a concern for me. I shoot 100 grn most of the time any way just because there are more available.

Personally I like 85 grn heads in a fixed blade with my set up, and for mechanical heads I like the 100 grn nail drivers.

My opinion is probably much like Arthurs, once you get into a "normal" length arrow and shoot vanes you should be looking at a 100-125 head.

Paul