Funny it gets a little cold up here
But i was looking at all the wasted light that hits my control wall ..... and it came to me to try a passive solar heater made for about 30 bucks
Increased my room temps enough to where i have to REMOVE unless its real cold outside
This was like a duh moment but i was happy to not have to run the heater during lights on
Im sure you could increase the efficiency of your heat by adding a thin layer of rigid foam on the outside of your tent..
And you could probably get a couple of degrees by putting a black trash bag on the floor of your tent.
It might work might not. But not more to lose then a trashbag and a days time to see.
But there is energy in light and that can be turned to heat with black and soloar absorbing materials.
At least in my room with my light adding the black passive heater worked.
Just my 2