Hello - I have a roundshot 65/220/70 and a Lookarund for testing
complete different stuff.

If i were you i would use the lookaorund-book-free for download now- to construct the cameras. alan has multiple versions there.
one can also use 35mm unperforated(better)-he shows also motor-constructions.

Roundshot 70/220 is working like this..
Yes film is pressed against a flat rubber-ring below. Pressure plate has one stiffer o-ring below and a loose thinner one above to press film against a second surface which is standing still against the film. Just talked to seitz about replacement of that main film-rubber-surface. is must be adjusted infactory to get precise distance to lens. Its a simple but delicate mechanisme. if the tensions are not right(worn-out o-ring) film-transport is not ok. One must work very precise.

film-takeup. its a special mechanisme which is connected to the main-o-ring.
except for the film-contact surface, all other rings are o-ring. two of them are holding the spool in place to avoid lateral movement.
vertically there is a spring-takeup for using both 220 and 70mm-spool.
btw: the pressure-plate has two positions for 220 and 70mm. the surface where the film is slipping over can be moved for 70m and 220 width. 60 and 54mm(53mm) images.
most interesting is how distances are set:
1. lens is shifted about 2-3degr. to increase DOF.
2. slit is moving when distance are changed. It will change the position towards the film/lens.
3. sharpness of slit is most important. there are instructions on the net how to do this.
If you dont mind carrying around large camera or weight i would get one of the roundshots 70/220 or better 220vr on ebay.

one can get filmslitters to cut down 70mm-film. Ilford announced unperforated delta 100 and hp5 plus for this year.

see here a roundshot-panorama- 4 secs around-1/60 second) 65mm grandagon.
www.auschwitzpanorama.tk