Achilles tendon trouble, from foot ascender

An issue has cropped up for me recently, regarding irritation to my Achilles tendon. I had been wearing some really sturdy Asolo leather hiking boots. However, the rear strap of the Pantin tends to ride up, digging in at the point where the hard leather and the softer cuff seam together. Using it in DdRT entailed a whole lot of foot pumping, and one day I noticed significant discomfort on the AT. I had to get another pair of shoes. It really doesn't bother me much now, but there is a thickening of my AT at that point where the strap dug in. I believe the sheath of the tendon is what's been injured, otherwise I really don't have any pain. However, I need to deal with this before it becomes so serious that I can't climb. I added a loop connecting the back strap of the ascender to the underfoot part, to keep it from riding up (see picture.) It's effective, but it keeps the ascender lower than than the ankle, which isn't good bio-mechanics. That ascender works really well right at the ankle. I'm continuing to work on this design problem, and would like to know if any of you have run into a similar problem.

That's an interesting solution. What if you added some cushioning to the back strap instead?

Thanks Bushwhacker, Maybe that's a part of it. I want to try messing around with the design of this thing to make it more foot friendly! It's such a popular item, for good reason, but I'll bet I'm not the only one who's had this issue.