I bought the Trumpet (H&L) and the Marigold (snaps). My little guy was born 7lbs 6oz 19.5 in. He is pretty skinny too. I tried to use this cover with a flat and also tried a bulky OS prefold and it is still too big. Just can't get a good fit. Tight on the waist but legs still gap even with the H&L. BUT I can totally tell that once he puts on a little weight they will fit great and for a long time since it has the snap down rise. I think it is totally worth it. You can't beat the price and very happy with the quality. Great product, definitely would be able to use from the beginning if you have a 8lb or more baby probably. To compare sizes I also have 2 RaR covers (fit much better, slightly big, but works) and 2 Bummis Super Brite NB. The Bummis fit perfectly but I can tell they won't fit for long (no snap down rise and already "fit").
I got these for the new little one. They were a bit bigger than expected so have to add more to make them smaller but once little gets a bit bigger these will be awesome!