Success: 3d printed and installed. You’ll note how I extended it for my 2.5" line, and added a window covered with plexi to view the action from. Only took a bit of sanding\drilling to get all the parts fitting together correctly.
I should also note for future users, M5 45mm screws work for everything, with 4 nuts. While I could have drilled out the four holes in the top blocks to work with the M5’s, I instead just put some machine screws in there to secure them. And while I ordered some 20mm M5’s to use on the X stepper (so as to secure the rear beam), it turns out the stock ones push through just enough so that they’re not needed (although I may still swap them out when they arrive).
Question @jzhvymetal : I’d be happy to provide you the cad/stl files for the new shoe/window so you can add them to your thingiverse page, or I can make my own derivative. Either works.
And thanks again to @New_Brit_Workshop for the original design!