Welcome back. I'm glad to hear Snickerdoodle is doing well. I was afraid something happened to him.
I have a Ferret Nation 182 now, (you can also use a Critter Nation that has narrower bar spacing). My old parrot cage is now being used for a parrot (what a concept!). Reuben died and we have a green eclectus now. With this cage you will have to get the aftermarket metal pans if you go that route because making a custom floor for that one was a big job. Making shelves is dead simple. Just saw to length, drill holes in the ends with a regular power drill, they don't have to be perfect, screw in some stud bolts and you're done. Just measure from the inside of the cage up to the bars where the shelves will be bolted to. Before you drill place the cut wood into the cage where you want it and then mark with a marker where you want the holes between the bars. You'll want two bolts on the long end and one bolt on the short end on the front side. The bolts should be at least 1" from the edge of the wood.
This will prevent gaps in the installation that can be potentially harmful. With 1" bar spacing there's a lot of wiggle room but smaller bar spacings will require a bit more precision.
Use fender washers and wing nuts that fit onto the stud bolts. This can be done with any chinchilla cage.
You don't want to use a metal frame unless you know how to weld. Gaps between metal grating and metal bars are extremely dangerous. Use a solid prefabricated cage that is all metal, has about a 1" bar spacing or less, and go from there.
I have posted a diagram here:
https://www.facebook.com/photo.php?fbid=1459579484355695&set=a.1389112151402429.1073741828.100009109720588&type=1&theater