Looks like there have been some casualties to my vague and convoluted way of thinking about, and expressing what, I was wishing to accomplish.... I apologize for that...obviously I am the one that does not understand and lacks the experience to formulate the question.

I had initially made the assumption that the segments of film had to be in the same holder in order for the registration of the edges to link up precisely... as they were to be contact printed then blended. This also seemed to me to be the way to keep the visual perspective when using movements. It also seemed to me the way to keep all the elements organized. I also had other idiosyncratic aesthetic reasons...... if you refer back to my original question it is apparent that I was unaware of the concept of darkslide masking as a means of gaining different exposures.

For me there are now some wonderful new possibilities and methods that have arisen from this thread that I can explore with masking as well as simpler approaches to the colour and B&W mix. Thank you all for your kind input and creative solutions.