I've used flats a couple of times with Oliver - I use Wonder Wraps covers as they are OSFA. Terry is very bulky though, so you might want to grab some flanny flats too. I made my own AIO's with the Honeyboy pattern, but there are free patterns online - mine work out about $7 a nappy. I have to change them just as frequently as flats though, and they takes ages to dry.