Exhaust Pipe Fittings

So, Toyota in it's divined wisdom has funky sized exhaust pipe diameters.

I have a 2012 5.7 Double Cab. I ordered a complete cat back system, but the flange size of the new exhaust that mates to the stock flanges immediately after the cats are 3". So much for bolt on. The stock flanges are rusty as hell so they need to be cut off anyways. The stock pipe OD after the cat is 2.16 for the passenger side and 2.31 on the drivers side.

After cutting off the old cat side flanges I plan on using exhaust pipe adapters(attached picture) to go from the stock pipe to the new flanges. My problem is the closet inlet(cat side) size I can get for the pipe adapter is either 2.25 OD or ID. I've never done any exhaust work, but my thought would be to get the pipe adapter with the 2.25 ID and cut slots in the pipe adapter so it shrinks on the passenger side, and then cut slots in the stock pipe on the drivers side and bend them in a little to let the pipe adapter(uncut) to slide over that. Going to use generic pipe exhaust band clamps to attach.

The other problem is the flanged side. I watch a couple videos on how to flare out the pipe adapter to hold the new flange on and that's pretty straight forward, but my problem is the pipe adapter is a true 3" OD and the new cat back system the 3" pipe is tapered down to 2.75 just before the flange. The specs for the flange I'm putting on the pipe adapter has the correct bolt pattern, the pipe and the hole in the flange will be 3" and not 2.75 making for a weird transition from one to the other.

I think this approach will work, but would love to see if someone else had to do this and has a better solution.