I have one that is almost identical except for the weight (60# @ 28"), and it seems to shoot well at 7" measured from the deepest part of the dish in the grip. I haven't experimented much with brace height yet, as 60# is a little more than I'm comfortable with, and by the time I've strung and unstrung and shot a few arrows, my muscles get tired and I have trouble getting it strung again. All that said, 7" seems to work well. Mine also seems to prefer arrows with a 50-55# spine.
RonP