Well here's what I'm trying first. I rolled out to the box stores today and picked up a couple of cheapo digital min/max/current thermometers and one big dial thermo. The dial one is for the shop so I know the temp in house. One of the min/max thermos went into the hot box. With two 100watt bulbs running in there and a shop temp of 55deg the box temp was 92! Warm enough.

I also picked up a sheet of foil backed 3/4" styro and cut filer pieces for the four ports in the cabin, one for the main bulkhead, a piece to fill the opening from under the cockpit and one that covers the main hatchway. I put 3 more reflectors with a 100 watt bulb in each securely clamped in the main cabin and closed her up. After about 45 minutes we were up to 60 degrees. I will swing by the shop tomorrow before work and note the max and min temps. Fingers crossed.