Paddington will not poop on his pad either. He pees on his pad, but poops outside under our deck, or if we don't see that he has to go he poops in the laundry room. Both places are very secluded, whereas his pad is in the hall bathroom (central to the house) I think this has a lot to do with it- he wants his privacy for #2! I wish I could train him just to poop outside though, rather than the laundry room!
-O