Thanks for the condescending tone and implying I'm too dumb/lazy to do my own legwork. Also, way to write out all that mess (you get points for good grammar/spelling at least), just to contribute nothing in the way of a solution.
If you had used some brainpower yourself, you would know that it doesn't depend on the conditions you stated, because the XLR has an adjustable cheekpiece, and a tubular forearm, so ring height-cheek weld match up and barrel contour are irrelevant. I need a ring height that will clear the forearm, and I can just lift up the cheek piece to get the cheek weld I want.
There IS an easy answer by the way, which is why I crowd sourced my question here on the forum: Someone may have this combination of mass produced hardware, and be able to give me the answer I was looking for.
I did do the measuring, and I need about .2" more height. But that's hard to verify at the moment, because the XLR forearm tube requires the rail be chopped short, so I can't get a good measurement, and I don't want to waste time & money on rings that will be 'close-ish' but not actually work.
So to clarify: I asked hoping someone with actual hands/eyes on a relevant configuration could provide me with some useful input.