Measure both palm circumference and length from base of hand to tip of fingers. The measure in inches is your size. If the two measures are very different, you'll need to decide which is more important.
I'll add that I came up with an ~8.7 for myself. I went ahead and purchased the peccary in a size 9 and it proved to be spot on, not "too big" but just a touch roomier than necessary which was fine by me.
Greg, what size was that green TS(S) jacket you tried on and posted the other day? 4 or 5? Also, is the length from bottom of the collar or top?
How about sizing on the Niche army green shirt jacket? Would XXL fit you or is it too small for you?