Do you think a 6" brace is going to be too short, or is it more subjective than just brace height?
Try this: Put your heaviest hunting jacket on. Get in a tree stand and set up a target to your far left (assuming your right handed). Make sure you're turning your upper body as far to left as you can on the shot. If your string hits your sleeve on the release, you've just missed that big buck because your brace height was too short. Do you really care how fast your arrow was going on that miss?