My not so little newborn was a 9 and a bit pounder. He was still too tiny for my OSFM AIOs or pockets for ages.
I don't own any greenkids, but can you make the rise any smaller?

Nate is 11months old and still has his bumGs and HappyHeiny pockets on the smallest setting fir rise (he's not the biggest kid but he is nearly 1).

I found when he was really little that the really soft fitteds were the way to go, with a cover to manage that newborn poo. Ones like Tots bots, spunkybutts fitteds, Cute Tushies Bamboo delights. I do have BBH fitteds but they are better now - they were way too bulky on a NB.

There are plenty of websites out there that will give you directions on prefolds. One of the girls on here makes them and sells them and I'm sure she'd be more than happy to give you a hand. I can't recommend Maz's covers highly enough either.

They are really easy to get used to. Even DH manages and we've used cloth on both our kids. I didn't even prepare him, lol. I just bought them and told him that's what we were using. As long as I have them set up ready to go, he's fine. I jsut used to lay a fitted or a prefold in a cover and he'd know they wen't together. I found it easiest to do this off the line. I still do it. I just keep all mine ready to go in one or two of those tub trug thingys.