Hello There!
I use belly bands on mine when we go to someone else's house, and on my good friends dog when he I babysit him. He starts marking the minute he comes in my house even though he doesn't do it at home. I've notice that if I leave the pad on him for longer periods of time, his little belly gets irritated. So, if you use belly bands when he's out of his pen, just make sure you check the pad pretty often to see if it's wet. If it's any consolation, my boys are neutered and still mark occasionally. They have pee'd on my bed a couple times, it's usually when I have a down comforter on the bed.
Good Luck with Toby!!!!