Jerold, I only want to use this for film, so I used the largest food tray available, which will take an 11x14 Jobo drum. Since I max out at 8x10 for my film, this isn't a problem. I have used an expert drum, but like the 2500 and 2800 series drums for film. Obviously if someone were going to build one themselves, they should make it to fit their needs. As the last image shows, I can get 5-6 glass beakers with the chemicals into the water bath for tempering, and yes, the heater uses a thermostat and is adjustable. I paid $20 for it. I agree that more universal connection to the motor would allow several types of drums to be used, but since I only use one type and diameter, I designed it for the quickest and easiest type for my workflow.
Phil, no I don't have any plans, as I have made it up as I went along. But I can tell you what parts I have gotten if you need it.