Ok, so I have been having problems with the endpin on my bass. Especially when I start slapping, the endpin has a tendency to slip, so I may find myself playing a good 3 inches shorter than when I started....does anyone know of a way to prevent/fix this?

I had a Goetz endpin put on both my basses, no problem w/ either slipping. Bob Gollihur might be the guy to talk to--

you should have notches in your endpin. Make sure the screw is aligned with one of the notches...don't screw it in too tightly. Push it up or down a little to make sure you have it at the right point, then tighten it all the way in.

If your endpin isn't notched...get one that is.