Update: so I also dropped this question to Bernie at Super16 since he's a stand-up guy and will be doing my U16 conversion. Anyway, he said it would work so I got some close-up lenses, and per the usual, he was right on the money. I did an eyeball test indoors while looking through my 10mm angenieux, wide open at 1.8, and the image was soft, but add one +4 close-up lens and pow! It snapped into focus. I still need to know how close I can get and to do some film tests so I'll post again once that's done.