I'm playing my Warwick thumb b/o last night, practicing my double thumb technique and all that, and I look down at the bit of heel that is just beyond where it meets the body (this is the side of the heel, not the back), and I notice what looks like a crack. I've always been able to feel some of the seams since the day I got it, and this feels the same, but looks a little different. It's not seperating, but definitely looks suspect. So I check the opposite side of the heel and see/feel something similar. Huh..... Anyone else have anything similar on ANY bolt-on (not just Warwick) show up? Any idea on what causes it? Failure of the wood? Too much string tension? Should I loosen the strings whenever I'm not using it? Finally, how would you fix something like this? I've got some ideas, but wanted to check. I've had this one for about 5 years, and have been nice to it (no dropping, beating, etc.), and would be pretty surprised if it turned out to be cracking. I guess the only way to get a good idea of what's going on would be to take off the neck and check it out.