What an interesting combo you have there turtlendog. We have a C'Dale road tandem on order, our first tandem. We've only test ridden so far. Currently we ride our 1/2 bikes about 150-200 miles/week. We both use wired computers and Sigma PC14 HRMs. I have wondered about cross-talk with our HRMs when we get on the tandem. I was thinking my body might block out my signal, but that's probably wishful thinking. Even with our 1/2 bikes, sometimes when we get too close to eachother, our HRs go way up, above 200 BPM. MY stoker just says that I still get that excited with I'm so close to her, even after all these years.
It will be interesting learning to tandem together and working out a new set of challenges. Good luck and keep it up.