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.