Thanks for the tip on notching the film.

The anxiety was too overwhelming. I pulled the film early and developed what was there. The frame spacing frame to frame then, is 17mm. Giving about 40 exposures to the 27" of film. That will work perfect, having only to reset the counter once. 30" inches of 16mm wide film (+/- 1mm) is what I get when I split 120 film into four equal strips. I like how this is all working out mathematically.