The problem I've always had with reusable pull-ups/training pants is that at least the shell is made of cotton, and cotton wicks. You can put the thickest, thirstiest padding in the middle but that wetness is going to wick out. I've never found any product like this that can hold any more than the lightest wetting, and I've tried Klienert's, Wearever, Connie, Pete's, and Dri-Wear, Salk--you name it. Just about the only thing I haven't tried is BabyPants. I'm sure they're good, but I'm convinced they're going to have the same problem all the others have.
-RMS