Hey, zzzz, something else I've done: I use a box cutter to remove the heel counter around the area of the Achilles where the injury was located. I know, I know, I never wanted to become one of those loonies who cut up their shoes, but like I wrote earlier, I honestly thought I was done running--I couldn't finish distance runs, couldn't do any fast-pace or hill work, and couldn't race without taking at least 2-3 days off afterward while I limped around. Given the inflammation that accompanies the injury (why it's misdiagnosed as Achilles bursitis) and the fact I have Haglund's deformity, cutting out the hard heel counter makes sense. And I've found that as long as I leave a strip along the top of the heel area, I don't have any problem with the shoe staying in place while I'm running. I don't even notice it!
Also, I didn't run at all (for about 10 months--7 for healing, a few more just to make sure) while the Achilles was healing--for this injury, I just don't think bouncing your heel off the pavement is conducive to rehabilitation. Again, I know, no one wants to take time off from running. It's SO hard to get fit again. And it takes SO long (especially if you're a masters athlete). But you have to weigh the pros and cons. Pro: You'll have a healthy heel to run on again, without limitations in your training. Con: You'll lose your current fitness, and it's a long road back--one from which you may never fully return if you're older. Here's what I can say. When I noticed the rehab was working for me, I told a couple friends of mine who had also spent at least a few years suffering from "Achilles bursitis." I couldn't convince them to do what I was doing. Now, a couple years later, they're still hurt. And I ran a 15:42 5000 on the track this spring at age 55.
Look, I don't know how long you've had this injury or how bad it's become. But I can tell you that I came to welcome the stinging sensation when my heel dropped to the low point during the exercise, because I learned over many months that stinging meant I was going to feel better in the future. Of course, now I don't feel the drops at all ... you know, because I'm 100% healed. Good luck!