I insulated my 180 Mak with a product sold to insulate walls behind radiators and tried it for the first time last night; conditions were rapidly cooling, heavy dew which turned to air frost later on.
There was no heat plume visible in the o-o-f star image - promising! Looking at a number of key doubles (Epsilon Lyrae, STF 425, Delta Cygni and Lambda Cygni) results were near optimal from the start, and were as good as I've seen with the scope. The heat plume did return later on after I had been looking at targets near the zenith - I assumed this might be heat leaving the front corrector plate as the scope pointed upwards. It didn't seem to affect performance though. Even after nearly two hours, the corrector was dew-free although the outside of the scope insulation was dripping.
Before trying it, I was a sceptic (in the day job, it is my profession), but I must say I was impressed!