Open Pit Rotisserie Turkey

I have a motorized rotisserie I cook lamb on over open coals on the ground. Last year I tried to do my turkey but it was in the 30s outside and my bird wasnt done until 9:45 at night (we had a backup turkey we did in the oven).

I was losing too much heat to the cold air outside and i also had the spit too high for the first half of the cook. I lowered the spit and built 4 walls out of 2x12s and covered them with aluminum foil to direct the heat to the bird which seemed to speed things up.

I want to try again tomorrow but we dont have a backup bird and I’m nervous it wont cook in time again.

Any suggestions or advice on how long it will take? Im planning for 6-8 hours and planning on building the box again. I also have some sheet metal (steel) i can use to help insulate.