I'm currently building up the combing lip on my Petrel using 1/8" thick strips of ash and cedar. It was in using the spring clamps for this operation that I noticed that nearly all my spring clamps had worn through the poly tips. (Yes, I've got the Home Depot cheapos.) Since I was in the middle of this exercise, I simply pulled the sleeves of the handles, cut them down a bit, and put them on the tips. For a long term fix I might try the plastic tubing approach. It's the easiest. Thanks for the suggestions regarding what some would consider a pretty lame topic.
Jim