I'd like my 6 x 4.5 and 6 x 7 frames spaced out along the roll.
I think 12 frames of the smaller and 9 frames of the larger would
be good. I may switch to a glassless negative carrier and will
need a certain amount of margin at each frame's end.

Each of my cameras has mid-roll removeal provision. Some
knowledgeable fellow might make the mechanical adjustments.
Any suggestions? Dan