A thermostat regulated UTH shouldn't heat the acrylic above 90F. That's not even warm to the touch. I can't imagine that it will off-gas at that temperature. If you use an RHP, that will heat the acrylic more, but, properly regulated, still less than 150F. I'd be more cautious doing that. I found this acrylic enclosure for sale on-line. They put an aluminum screen in the top for the heat lamps, so I suppose that's also an option.