Well, I think I trashed this set of boots. The heads did end up popping off after drilling considerably deeper than the picture with a slightly larger bit. However, vice grips could not get the shafts out- either the shafts were deformed due to too deep drilling with too thin of a bit, or the outer coating with scrape off, providing no grip. Dremeled the shafts relatively flat, but failed to drill new holes that were centered and perpendicular to the plane, though I did use a center tap and increasing bit diameters.
Anyway, now looking for a new pair of boots, M27, else my season is over before it even began this year. Let me know what you have...
Thanks everyone for all your help though. This certainly has been enlightening.