I used a brass rod, 1/2" dia and turned it down to 7/16, (except for the tapered head), Threaded it and bored 1/8 hole to accept the thermocouple. I cross drilled and tapped 1/8 hole for a set screw to secure the TC after protrusion adjustment to just clear the arms of the drum. The thermocouple wires were attached to a mini recepticle mounted to the back cover.

Care to log and post a temperature comparison of the HotTop readout and your probe temperatures?

Two issues I see :
1. The insertion depth should be about 10x the probe diameter.

2. The probe mount may affect the reading.

Here's a comparison for my 'old' digital HotTop:

Ian,

I spoke with the brains at Omega. They assured me that my installation is fine for the intended purpose and any mounting induced errors ( which are always present) will be very small, (0.5 deg F or less).

My roasts are done manually and I use the the probe readings to help me develop a profile. I am more concerned with repeatability then an exact temp reading.