How I came up with this is a long story, but I just started doing this "hack" and wanted to share.
Take an Alva 4.0 (the one with the crazy snaps and double gusset that isn't) and sew a snap into each of the four corners of the insert flap (I used the regular metal snaps sold on a roll from Jo-Anns, it isn't a perfect match the the G snaps, but it does work). Snap a Gdiaper liner into it. Stuff the liner with your choice of insert.
At the moment I have a M/L liner inside the Alva with it on the Medium setting (3 snaps up) and stuffing it with some random homemade prefolds. I'm planning to sew some fitted inserts for it soon.
You can use the Alva as a cover over and over.
The Gliner snaps are completely covered by the Alva's front and back flaps. !!!!!important!!!
More leakproof-ness around the legs of my skinny baby.
The front and back flaps also help contain blowouts.
The Alva 4.0 is cheaper than a Gdiaper cover.
If I decide I hate the way the gliner is fitting, I just take it out and use the Alva like it's supposed to.
If I need a super-simple diaper for a babysitter, I can just unsnap it and use the Alva as a pocket.
You could probably get away with also stuffing the pocket with something thin, like bamboo or microfiber, if you want extra protection.
One-size. No need to buy separate sized covers. As you adjust rise and width the liner elastic will adjust. (For the smallest setting you'll probably want the small gliners, but for the rest of the rise settings the M/L/XL liner seems to be best.)
Outside of the gliner there's only seudecloth or microfleece against baby's skin.
Um, it snaps. In the front. Like normal.
You have to sew in the snaps by hand. Getting the snaps right into the corner of the inner flap took some precision and patience.
Probably fluffier than using the Gcover.
The suedecloth/PUL isn't as breathable as the Gcover.
The Alva will probably get dirty if you get a major poo, and you'll have to throw the whole thing in the wash. (But then, I think that's true of most covers - and right now my baby's only pooping every third day or so anyways, so I'm not too worried).
Alva 4.0's have a small range of cover designs. And those crazy colored snaps - oy vey!
What I like most about this, other than it being economical, is how adjustable it is, and that now that my baby is only pooping infrequently, how little laundry it generates.