I often take a 400ft roll and divide it in Half for my Alden 200 Loader, which takes 200ft loads.
I use a set of rewinds and what is called a "split reel." basicly two flanges with a core that screws together. My seond rewind was for use with a syncroniser, so it has room for several cores or spools or reels. I sandwidch a 100 ft 35mm Spool, between two antique 200ft 16mm spools. (they could be reels)
stick the fresh film in the splt reel, and wind onto the 100ft spool, BUT keep winding until the film is up to the size of the 200ft spools. (all by feel in the dark of course) the film will be over the edge of the 100ft spool, but that does not mater as you are going to put it in the loader. the remainder of the fresh stock goes back in the black bag, and then the can of course.
stopping to the 100ft spool size, would also work. with a few more odd size final rolls.
with taking 200 ft off the 400 foot fresh roll, the next time I can just put the remaining 200ft roll into the Alden 200. I take a core saved from a roll of bulk still film to fit inside the one inch center hole of the 2 inch core the film comes on.
40 years ago I did make a jig to wind to a 200 ft roll. I just set teh rolls of a small piece of Formica countertop saved from the installation of a kitchen sink. the formica was slipry enough to allow the film to turn without the risk if it spilling.
looking up this item :
https://www.printfile.com/product/ap351000-35mm-1000ft-film-container/ we find a container for storing 1000 ft of processed film on a core, and see the internal diameter is 10.25″ so that is the ball park size of the raw roll.