Nope. I fold mine into thirds and lay it in the wrap. I have duos too. It does the trick really well. Organic prefolds seem to be much bulkier that non organic though.
I think in the newborn stage that snappis are especially helpful, unless you're okay getting poop on the cover every single time... if you learn the right fold and snappi it, very rarely will poop leak out of the prefold. If you just lay it in the cover, it will get everywhere. The cover will contain it, but it will get all over the inside. At least, that's what I think would happen in the newborn stage. Snappis are pretty cheap and learning the right fold and how to contain newborn poop doesn't take more than a few days... I thought it was well worth it.
Trifold means guaranteed poo on the cover for us. We use the Bummis wraps and it very rarely makes it past the cover, but it's annoying to constantly be washing the covers. I always used the snappi when she was little and pooing all the time. Now that she's more predictable and pooing 1-2/day, I can trifold when I feel safe it will only be wet.
Re: Do you need snappis for PFs....
SAHM to 4 kiddos... K (5/05), N (4/09), C (11/10) and Baby A 1/13/14
Trifold means guaranteed poo on the cover for us. We use the Bummis wraps and it very rarely makes it past the cover, but it's annoying to constantly be washing the covers. I always used the snappi when she was little and pooing all the time. Now that she's more predictable and pooing 1-2/day, I can trifold when I feel safe it will only be wet.