So I'm new to the whole cloth diaper scene, and I'm considering buying a few of Baby Pants' Training Pants. But, in order to wear them, I'll need plastic pants. I was hoping to buy their PEVA pants, but I have no clue what size to get. The training pants have a "fits waist size..." section, but I couldn't find one for the PEVA pants, just measurements. So, I was hoping for advice. It would be greatly appreciated!