Instead of buying yet another ball, I have been practicing using strike ball for the ten pin instead of my plastic ball which has cracked. I believe Norm Duke is one of the few pros who does not switch balls.  So far not too bad, flattening out a stronger ball isn't easy, but I think it's a great tool/lesson to learn (keeps me honest).  Anybody else, not switching balls for the ten pin, and what is your success rate with it?  Generally, I do have problems with the 10 pin anyway, but this is not really that difficult, and gets a bit easier as I go along.