On Tue, 25 Apr 2017 05:09:10 -0700 (PDT), TimR
wrote:

On Tuesday, April 25, 2017 at 7:37:28 AM UTC-4, wrote:


Not sure if there's a 2.5" I.D. female to 2.25" O.D. male adapter for sale out there, and not something that I can make with any practicality. Or maybe someone's done this already and knows I'm wrong about some detail here?

Actually, you can, quite easily.

Download some free 3D drawing softwa 123Design, TinkerCad, OpenSCAD all work well. Take the file to your local library and 3D print it.
I just chuck a chunk of ABS or PVC heavt wall pipe in my Myford
lathe and make what is required - - -