So I'll make a 5/8" hole. Probably the extra 16th won't weaken the floor so much that it will be dangerous.

I'll probably have to buy the bit for Victor, trade it to him for his using his hammer drill and making the hole. And yes, I am (with difficulty) resisting the temptation to buy my own hammer drill and bit and do it all myself. Figuring how often I actually need a hammer drill, over the next five years it would cost me about $30.00 per hole...

tanstaafl.