My experience using a BrewJacket Peltier on an Ss BrewTech 7 gallon Chronical was that it was an exercise in futility. I wrapped the Chronical entirely in tight fitting Reflectix for insulation, including the cone bottom and flat top. The only exposed areas were the bottom dump valve, the front transfer port, and a small hole for the temperature probe wire. While it does work, the cooling rod doesn't extend far enough into the wort to be even marginally effective, even when using the flat lid. Domed lid? Fuggetaboutit! It would take around two days for the fermenting wort to stabilize in the low 60s (ambient 70F), so you're already 2/5 of the way through a 5 day fermentation of ale. Plus the Peltier would run almost continuously. Getting the temperature down to 50F for a lager was even more frustrating. No way you'll even get it close to a cold crash temperature.
I always had better luck using a Better Bottle plastic jug with the BrewJacket. Still, the advertised "25F differential between ambient and max chill" is more like 18~20F on a good day. The BrewJacket is good if you're looking to keep your fermentation a little on the cool side, and the vendors seem to be reasonable people to deal with. But if you're looking to make substantial gains in your process you'd be better off by saving your $$$ and investing in a small glycol system like Stasis (if/when they get their act together).
That said, if you already have a BrewJacket, the jacket itself makes a respectable insulator if you invert it and put it over a stainless conical with a glycol chiller. Not much in the way of bling, but it can improve your efficiency a bit.
