Syncing the MOTU to timecode at its 29.97 fps setting while sending it 30 fps seems to me like a brilliantly simple way to get it to record at 48.048. When I first got the MOTU I experimented with this too, by recording pieces of audio of known length in this manner and then comparing the recorded version's length to the original. As far as I could tell, it was a perfect .1% change. Since I just do commercials and video, no one's ever asked me for 48.048, so I've never gotten to really test it either.
I know this doesn't help you with the other settings you'll need to change (or not change) in Boom Recorder, but if you're going to do tests with a post house, I would be very interested if you would test this method. Respectfully, it seems as if people who have never tried it are saying that it won't work.