Hey guys,
thank you for all your feedback. Encouraged by the reports that a CycleOps fluid works on a 145mm spaced tandem, I got a used one today. Still need to find a matching skewer to really try things out, but it's looking good so far and I have had my road bike on it already. Now, I have an entire season to figure out the best approaches to make a regular indoor cycling exercise as most fun as it can be - while soaking up the wonderful May sun, outdoors!
There was an older 'smart' trainer for sale within our price range, but things didn't work out and some hacking would have been required to match it up with Zwift & Co. Hence: let's turn to Star Trek. Energize!