Good job Paradigmnoia!
I snuggled in the 2.2 k resistor into a new RS232 header along with a 1K in series with the DTR lead, and installed that into a gutted VGA header housing. Shoe Goo used to back-fill converted DB9 housing (hood) to keep the TX resistor and entire RS232 connector from pulling out of cable.
Next a Sparkfun RS232 to TTL converter was bored for a crimped and soldered lead to the DTR pin via the perpendicular bend at the back of the RS232 DB9 connector, shrink tubed over the main board, Molex connector aligned with the 4 other pins, and supported with a blob of shoe goo.
The Reed data logger basically sends data words non-stop. One word for each thermocouple, each apparently read at the instant before reporting the word. I was turning the DTR off, changing the thermocouple from one to another TC port, heating the TC with my fingers, and turning the DTR back on again (which turns back on the data stream). The next reading for the changed items had the changes immediately effected in the data. This seems to mean that there is no large buffer in the Reed device storing up any information long-term. There also seems to be no simple way to get the data sent from the Reed to begin with the first TC first, when receiving it, so I probably need to parse each word, update a bunch of registers, and at each time stamp event read back the most recent temperature registers in the right TC port order for the Arduino SD data log spreadsheet. It is tempting to spy on the Reed data feed to the SD drive inside of it, instead, where temperature data is already processed into the right order for its own spreadsheet.