Im looking at getting another snake, and I was wondering if you can safely use a UTH with a plastic tub? (regulated with thermostat)

I have a reptitherm 500 and a 10-20 gal UTH on a 20 gal long glass tank, and im adding a large sterilite tub with a 10-20 gal UTH identical to the glass one.

2 questions

1.) will this melt the tub if its regulated between 89-95 degrees

2.) can you use one reptitherm 500 to accurately manage 2 identical UTHs or should he get another thermostat. (obviously the glass/plastic and thickness will change things a bit, but both will have thermometers and will be regulated accordingly.)

Thanks!