bobr,
just guessing, but from my recollection of how the ELK is setup for a thermostat(s), it is for one flavor at a time.
If you are interested in selling the TR40, give me a PM. I have a TR40 in my house and now need either a TR16 or TR40 for my barn. Don't need a TR40 (over the TR16), but if the price is right, might help both of us.