I also agree that you are probably a little long on yoru draw length, EXPECIALLY if you are using a release aid.

I try to shoot with a slightly open stance, my feet are not perpendicular to the target. That should help out. From a tree stand you dont always get to choose how you stand. Practice good form!... The way I look at it. If you dont wear an arm guard you deffinatly get negatice reinforcement if you do hit your arm. I do wear an arm guard when wearing a coat. Just to hold my sleave in!