How cool! Thanks for sharing. I'm actually in the process of doing something similar myself. I bought some cheap Hello Kitty panties and some zorb. I'm sewing zorb into the soaker area ( on the outside). I did the first pair today! I may add a fold out layer as well. Your prefolds will be much better than my zorb for catching pee, I think. But my prefolds are far too crunchy for against the skin.
Do you have pics?