You could always email RJ Mical... OK, I'm only kidding but didn't he co-create the 3D0?
I think I remember him discussing it in the interview that was posted up here a little while ago... he also created or co-created the Atari Lynx - I always wanted one of those - I bet they look really dated now...
Good luck with your search for a solution... seems like the N64 problem with picture output is the same for this machine... RF sucks...!
Maybe I will hunt down a moded NTSC N64 one of these days... I wonder if someone has attempted a picture output mod for the 3D0?