We have also been using the disposables that I bought from RDB911

. They are great! However for some reason Bayleigh decides on some days she wants to destroy them. So, now I am going to order the washable ones from Ryan too. His prices are great! Good luck to you.
I was wondering, why do you feel you need to put the pad in the litter box? It just seems that is too much for a little puppy to do. It needs to be easy for them & not anything to think about. Climbing up in there is probably too much of a chore. Just an idea.
Good luck to your training!