I have a carbon fiber Newtonian that is insulated with bubble wrap on the outside. But I still have problems with the primary mirror getting dew after a few hours, or rather, it seems like a hazy pre-dew that bloats the stars a tiny bit, but never develops beyond that into water droplets. (or maybe its micro ice crystals) Anyway, I read about a few different dew prevention methods, but which one is good about not making tube currents that mess up the seeing? I recognize that you are only trying to barely heat the primary to or above ambient temperatures to avoid this.
a) heated dew shield or front lip of telescope - that seems like it would create heat waves in front of the telescope
b) blow air in thru the back and out the front. It does create turbulence inside the tube, but maybe that isn't a problem because the air is at a constant temperature throughout
c) evenly-spaced heaters on back of primary mirror. Maybe if you apply low enough power it won't warp the mirror, nor cause that boundary layer "steaming" in front?
d) heater wrapped around back part of telescope