Heat worked to free the HBA from the shield! Thanks a bunch to SBT, I was skeptical, but I'm also cheap. I took the weekend off from working on it out of frustration. This morning I found a small pipe soldering propane torch in my garage, and thought what the heck. I applied heat from the back for about 30 seconds and then realized I should have removed the rubber plug for cog access so I stopped, gave about a dozen whacks with the slide hammer and it came apart to my surprise. Shield still looks nasty, but a little paint might improve things. Like I said, I'm cheap.