Anyone remember flexible cylinders? Why were they flexible?

In the 1970’s, maybe 80’s, there were penis pump cylinders with a certain amount of flexibility. Because they were flexible, you could compress the penis and basically jelq it inside the tube with most of the force of the pump being exerted on length. I don’t know if they were DIY cylinders or a commercial product, or if the flexibility was a defect or a deliberate design feature.

Does anyone remember these or have experience using them?

Was there an advantage to using them over the hard walled cylinders we have today?

Does anyone have any experience with modern replications of these flexible cylinders using something like large diameter hose you can get from a hardware store?

I think there might be an advantage to this design, but want to collect information about it before adding it to my list of things to test out. Maybe there’s some major disadvantage to this design that I haven’t thought of yet.

In addition to the possibility of jelqing under vacuum being beneficial to gains, I’m interested in the possibility of shaping the penis to have an upward bend. Large diameter hose tends to have a set bend in it from being on a spool, so even if jelqing in the tube is not productive I could prep for my post size goal experiments on changing the shape of the penis.