So you think a internal coil is the way to go on a conical?
For the Fast Fermeter, yes I think this is better. With the large handle valve at the bottom and the thermowell midpoint, a chiller wrap would have to be semi permanent. Plus it's plastic, so not the greatest thermal transfer.
The heater wrap I made has the film running at a slight angle top to bottom so I can have a way to open it to get it on and off easily.
For +/- 5 or 10 degrees a wrap might be OK, but a greater differential, fermenting lagers, cold crashing, or lagering, for example, I don't think it will cut it on the outside.
Another design I've considered is a solid cylinder with the tubing wrapped around the outside, top to bottom (50ft+). Then you just lower the carboy into it. Down side is that you don't get the tight direct contact, but it's more like a mini fridge so maybe it would work. Still pondering this design.
You can see many of my projects on another thread, suggesting continuing this diverging discussion
there, and turn this back over to the original programming, pond pumps.