Saltshaker,
I just reread all the posts in this thread, and we all wound up sounding disapproving, and I'm sure none of us meant to be.
Playing around with stuff is fun, and it's how we learn lots of new things, and grow to understand more about this crazy hobby.
I think we just didn't want you to ruin a good lure without a good reason, and wondered if you were trying to achieve something specific, instead of just experimenting as a learning tool.
In my experience, shaving or reshaping the bill on a store-bought crank doesn't improve it. The lure companies have designed that bill to get optimum performance with that bait.
But I did try it anyway, and learned some things about how lure shape affects both a lure's action, and how deep it dives.
So I wouldn't discourage you from doing it, if the lures are truly beyond saving, as you said.
My test baits were typically Rapala DT's, because the bills on them broke so often (Grrrr!!!!).
I made a wake bait with a DT16...failure. I tried to give it a smaller bill...failure.
I got some DT16 bills from Predator Bass, and put the same size and shape bill back on the bait, and it worked great.
Through all of that, I learned more about how bill shape affects performance, and how bills and ballasting are inter-related.
So it wasn't a waste.
Good luck.