hey trapper,
I can give some info on the cab temp. I do not have doors but just putting the cab roof on with the windshield provided a lot more heat. There is some draft spots for sure, but the engine heat from under the seat was more helpful than i expected. I added the heater and had the original kit and recently i had the revision done. The revision really works well and even with no doors i was warm driving around with my gal... and she loves it. I am not in sub zero temps tho. I get out in it in the teens and 20s and feel fine in light gloves. In the 30s i dont need gloves at all... and like i said, no doors at all. I also saw a small 12volt heater at harbor freight that could be set anywhere if she wants more heat. It was only $15. if you are in really cold country, you can also get a 12volt electric seat pad online or at walmart for $20.
From what i have heard, both the hard and soft doors have gaps that some chase down and others find no problem with, plus there are gaps in the levers and steering, but i really am warm inside and to me its just the occasional side wind gust that might bother someone in colder weather. I do feel gusts with no doors but i stay warm with that heater going. The vents install on the lower side of the dash giving two for the legs and two about thigh high. I think if you have any type of doors, you will have plenty of heat without having to close the gaps. My gal loves it so much she asks to go out in it at night year round even in the cold anytime we can.