I battled the same problem with a friend's Drenalin for several wks. this past summer. I was helping him set it up and after adjusting for optimal arrow flight we noticed the same problem. He also shoots an HHA optimizer and uses the outer ring to line things up with his peep and just like you part of his sight ring is covered by the riser. I'm afraid you're going to have to live with it. I agree that adjusting your rest away from centershot to compensate is definitely not the way to go. I think the problem is the 2" diameter of the HHA sight ring and the only way to overcome it is to change to a smaller diameter sight ring.

Dan