EV is just a radiant flux density (brightness) and where it will be placed tonally depends on your exposure. For reference, say something is EV15, it will be middle gray if exposed at f/16 t=1/ISO. I was planning on exposing the disc at about +3, i.e. setting the camera+filter as if the meter reading had been EV31, which would put the sun at Zone VIII (close to but not quite paper-white) on a straight print.

Anyway, my shoot-through-IR-filter experiments failed, mostly because I had someone else perform the tests while I was off at work during the day when the sun was out. Apparently there might have been a cloud involved

Transit has been going for about 75 minutes so far and we're still under 90% cloud cover. I have my hopes up and the university just down the road has announced that they've publicly-accessible scopes setup this morning, so I'll go there once it clears a little. I'll probably just end up with a digital macro photo of a projected image.