Re: probably a stupid question......
You can lay a piece of thin fleece as a liner between your babies bum and the fitted like a liner. Bum Genius Stay Dry Doublers are a layer of fleece and microfiber that is nice to add a stay dry feel (this might be too bulky under a fitted). Also, if you can track one down, Chelory has a stay dry ultimate fitted that has a sport jersey that is stay dry
Caroline Psalm 139:13-14