1. It really depends on the area you live in, and the temps you keep your house at. 72* is a little cool. Might be worth getting a low wattage infared light to keep your ambient temps up. You don't really need a second thermostat, but you do need something to control it with. I prefer to use dimmers with lights. You can pick up a piggy back dimmer from the home depot or lowes for around $10. It's a little dimmer slider that you can directly plug something into. No wiring required.
2. No need for a liner. Just the aspen is fine.
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