Nice solution. Just a word of caution on the split USB power. If you are also splitting the AC reference, and you have not yet seen smoke coming from one or both units, you probably have the polarity correct. However, this configuration puts both units on a common ground and can cause the two to basically fight over over any minute differences in bias voltage. I don’t recommend you leave it this way long term. Better to add an independent USB power to one of the units.
I can think of a couple of ways to add temp, but if you are a tinkerer, here’s how one user did it: