We use a service with prefolds and a SWW over them. We use a snappi and have to pull it so tight to avoid leaks. Then, we have to pull the SWW very, very tight to get it around his little skinny legs. It's as tight as it will go, actually. With the velcro all the way to the middle of the diaper. He has a skinny waist as well, but the diapers seem so tight. He's 9 weeks, about 13 lbs. and we use SWW velcros in a size S. The prefold seems to loosen up a lot once it's wet. I think when he poops after peeing, then we get poop in the cover, but that's beside the point. My DH is worried that having such tight diapers is dangerous (as in squeezing his body so much that it stunts development!). I don't think it's that bad, but otherwise they don't seem to work.
He always has red marks. I couldn't imagine not having them and actually catching any pee or poop.
Is this a problem for DS? Any solutions or reccommendations? Also, we get poop inside the covers almost every time. It's not that big a deal to me, but would be nice to avoid.