I did, it does heat up the sleeve directly. When it shows 80 degrees I am pretty sure the sleeve is also close to the 80 degrees.

The EBIS just has 2 heaters hanging in the oil with the temp sensor of the heater nearby. That is important because the heating is slow and if the temp senso is too far away from the sensors it will become very hot arround the heaters with the chance of burning the oil.
But that is why the EBIS has a 2nd temperature reader, that will read the oil on the other side of the bath which will give a right indication to start the electric motor.

I have some material to make 2 new ones, I think I will mount the heaters and the temp sensor on the frame holding the motors.