You don't even need a TBE. My home made version is a picnic cooler with a fish imersion heater in the bottom. From looking at the Jobo specs for the TBE my setup is better -) I use Jobo 2500 type tanks on a Unicolor motorbase. The tanks once preheated hold temp very well. C-41 developer is only 3:15 but the tanks hold temp longer then that.