That I don't know, I don't have any 4-20's. I'd suggest contacting John and asking.
(Oh, and resist the temptation to "just try and trim it a little" with a Dremel or something. It'll just turn into a dog's breakfast. (Don't) Ask me how I know......)
@[email protected] ; Are the ocular diameters/dimensions different between the 4-20's and the 5-27's ?
@Krob95 ; IIRC, the ring body was not difficult to install onto the scope's ocular. You will find the caps are stiff on opening/closing, particularly when new. I put a very, very small amount oil RemOil around the inside rim of the cap itself with a Q-Tip. Makes a world of difference. With time, the caps will loosen up. Your choice as to whether you want to lube them or not. Use any lubricant sparingly, you don't need very much. If you do apply it (with Q-tips), you'll be picking a little fuzz off the caps. Also no biggie.