When I got my Takeuchi thumb I should have planned it out a little better. The thumb tines hit the bucket teeth instead of meshing with them. I find this annoying because I can't grip a log that is smaller the 12" in diameter. It just slides out. Unless I pinch it between the tip of the thumb and the tips of the bucket teeth. There's probably no quick fix for this, short of a new thumb or bucket. Something to think about when getting a thumb.
Yeah that sucks. 3 solutions - new bucket, new thumb or gas axe and welder. None of those are inexpensive.
Cut the thumb tips off and burn out two new ones out of 1"plate that are 4-6" longer and over lap them on the outsides of the thumb 4-6" and weld them on. A little scrap plate/flatbar and about 2 hours work and your done.