Try not to bend your arm when you shorten up. Anchor point is a very personal thing, but depending on the bow you are shooting, it could be the cause of your problems. I find that with proper grip and form, it is much easier to shoot too short a draw bow than even a fraction too long. I get plenty of arm clearance. I think a real good indicator of proper draw length is actually where the arrow nock ends up when you draw -- shold be nearly directly below your eye with your head upright. Short A-A bows tend to play havoc with comfortable anchor points causing guys to get bows that are too long.

When you get too short, your sight picker will tend to become herky-jerky in movements. Too long and the pin will slowly float but not really stop. Just right and the pin should float and then stop for several seconds.

On the link, I find the recommendation to put the thumb behind your neck to be a bad idea as that causes tension in a lot of places you should be relaxed.