I fermented in carboys in the same chest freezer that served as my kegorator ... set at disepnsing temps ... each carboy would wear a thin-film heater, a neoprene carboy jacket
Must say, I never would have thought of that. Novel. Like the pics, too.
There would seem to be a trade-off ... if the neoprene doesn't insulate well, then the heater is making you burn more energy keeping the freezer cold. But if the neoprene insulates too well, lagering and keeping a vigorous fermentation from heating up would be harder.
I used to lager in a dedicated (small) chest freezer, and even without neoprene I still wasn't happy with my ability to control the fermentation temperature while the yeast was working. There is something to be said for water jackets instead of air ...
Did you notice any of these issues, eg your freezer having to work harder? Did you experiment at all with different insulation around the carboy?