Is he being scolded at all for peeing on the edge of the pad? If he is, I just wonder if he's getting confused on where he's supposed to be going.
I think I posted in your last thread that we were having "edge" problems too, but have now completely solved that with washable pads. But when we had the paper pads, Coby got a treat for even "edge-peeing" because I was afraid to confuse him.