Any reason why you're doing the internegative by projection rather than contact? I'm just curious, because I have some 35mm slides I plan to convert the same way, and TMX was my target as well.
Well I suppose I could just lay the 6x7 slide onto the 4x5 film in total darkness, and cut it out later. But I think I'll have more control with enlarging and have a bigger neg to play with later. Make sense?