Thanks mrmo for an island of evidence in a sea of anecdotes.
Looks like 10km male veterans is the only case where the tandem was quicker.
Everyone else seems to backing up what I have heard elsewhere and found ourselves.
Good point about the top riders not riding tandems. I guess it’s a bit like singlespeeding. If you’re good enough to be in with a chance of an overall win, then you go in the open class, not some sub-niche.
Finding two riders with compatible styles could be another factor too. I tend to lunge up and down on the pedals, while Mrs MTG spins in circles.
I feel I’m being carried through at the top & bottom, while she feels the pedals are pulling her feet away on the down stroke.
We’re still experimenting with hill climbing. Mrs MTG is getting more confident and trusting and will stand on some climbs while I sit.
I don’t know if I’d want to try that with someone nearer my size on the back though.