Eyepiece Diopter on Canon 7 -- hack one?

[pagpow]

I'm slowly putting eyepiece diopters in my RFs. Unless I'm missing something, the Canon 7 has neither built-in nor add-on provisions. (I know I can see the viewfinder with my glasses, but I want to avoid scratches.)

Has anyone tried installing a threaded ring around the eyepiece and using a Leica or Epson diopter? anything else?

 

[pagpow]

Oops, I thought the earlier one had not posted. Sorry.