Depending on how your engine is hanging off the nose of the plane and what structure is located where, I've found a propane torch is invaluable at pre-heating the engine. I've used that method to pre-heat Cox .049's and flown at -10F. The engines started right up on the first flip since they where close to operating temp.

Performance of the plane and engine is much better in the denser air, and ski's are a blast to fly with. Floats will also work on snow.

Hogflyer