T-4 with a 210mm wheel installed...
T-4 210mm wheel.jpg
... only "mod" was to put a small block under the water trough to raise it up. (I also put a piece a tape on it so it wouldn't move around during use.)
Only downside is the stone has to be removed to install/remove the water trough.
Sharpened a couple of knives, didn't see any issues. (You might need the longer USB for some knives?)
(Do I have hard water?) ::)
Edit: Thought I'd add a link to another post where a SG-250 wheel was put on a T-4...
https://forum.tormek.com/index.php/topic,3344.msg20259.html#msg20259
Hmmm...interesting. There's a used market, or at least a second life for the 250mm wheels after they get to small for the T8.