If you can come up with some heavy dark colored cloth to line the backside of the burlap, it will help hold in the heat or block the wind out some.... especially if your using a Mr. Heater while your hunting.|
A piece of heavy mil plastic will make it more water-proof and keep you dryer.
If you go the heavy cloth route, spray it down or soak it in waterproofing solution and that might be the best of both worlds.
Looks good so far man!!
But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.