Vacuum Former Build Questions

Hi, looking to build a vacuum former loosely based on some designs that I've seen. Thinking around 24x24. I have a number of questions I'm hoping I can get some input on:
1- Heating elements. Is there enough of an advantage to justify building your own elements with coiled nichrome wire versus cannibalizing an off-the-shelf quartz space heater or three?

2- What about temperature control - for various plastics is it worth the effort to use thermistors and PWM temperature controllers or is that just overkill and heat-it-until-it-sags is all the control you need?

3- Anyone have a quick release design for holding the plastic sheets that you really like?

4- Related, what about a design to use larger and smaller sheets? I want the large capacity but will often be doing things much smaller and don't want to waste a lot of material. I'm torn between whether it would be worthwhile to make a couple sizes of plastic holder and have block-off plates for the vacuum table or just build a smaller machine that runs off the same vacuum source. Thoughts on this?

5- On the vacuum side is a 5gal accumulator large enough? How many inches of vacuum are needed for a reasonable DIY machine?

This is new to me so I appreciate any input.

Hi Cal - Vac forming has a few issues:
1) The plastic needs to be dry so you will need a dryer to condition the plastic before you form it
2) The best way to heat the plastic is to use tuned ceramic heaters like these https://au.rs-online.com/web/p/heating-elements/1988529 these are more efficient then wire wound elements. They generate IR directly.
3) The heat pattern has to be very uniform and non contact temperature measurement is best. If you can find an infra red camera then you can see how even or not the heat is
4) Usually if you have a big machine when it comes to small parts you make moulds that have 2 or 3 moulds on it so you get more than one part per sheet. Trying to vary the sheet size is a tough issue to tackle
5) Look up commercial machines of similar size to what you want to do and they will spec the vacuum size and accumulator size if used. A small vac with an accumulator will have a slow cycle time. So depends on what cycle times you are aiming at. or you go with one big vacuum (no accumulator) to get short cycle times

good luck - Peter