Hi and welcome to RCU and the addiction Allenmr.

I would say two things mate. In those kind of temps (around zero f or so), I'd try and heat the engine up with a strong hair dryer or heat gun prior to starting it. Then as soon as your engine stops, make sure you position the piston at BDC of stroke (bottom dead center). That way your sleeve can cool down to it's original position without being impeeded by the piston itself. Also, you'll want to use a very hot glow plug.

(I'm wondering what happens to fuel at those kind of temps or the oil viscosity in the shocks and diffs??)

Good luck and enjoy.