I took a grinder to my HF iron. The part that hooks around the rim is cast wrong, at least from my experience with manually busting tires, so I modified the inner contour so it stayed on the rim better, and allowed more force to be put on the lever.
I also found that putting a piece of pipe on the part that still stuck up, and having someone hold it vertical, instead of allowing it to twist out from under the bead, helped a lot. If you've got the feet anchored SOLIDLY into the cement, and you know that the thing won't twist, you can do a lot. the anchors in my floor started coming loose after awhile just from the twisting motion. I think if the foot plate had the flat part against the floor, rather than having the ~1.5" of open C-channel, the anchors wouldn't move sideways as much, and keep in the floor better, too.
---** To be in compliance with the Anarchy **---
Jorden R. Kleier
Baraboo, Wisconsin, USA
1990 Mazdog Protege 4WD
1973