^ Yes and no about that. I've had some time on a Cannondale aluminum and our early steel Santana.

Starting in the very late 70's, let's just say early 80's, there were only a few but some with significant changes in tandem design. Shape of the boom tube, tube specifics, diagonals. Biased here, but Santana is a good example. If not counting grams, the ride is just absolute the most plush two wheel machine. There's only a nominal flex that is likely on par with most of my better solo bikes. A team with smooth cadence is crucial too.

Largely though, its what one perceives as flex. You can have the stiffest tandem frame made but because of the wheelbase, the weight of each rider plus add their body movement / inertia motion, most solo riders first think the frame is flexi.

What really is a mind pop is having the chance and invite to ride a state-of the-art new tandem. Two fairly strong riders - the power transfer, lightness, especially for climbs are incredible and a treat. No, should say awesome.

But then to get back onto the old Santana is like a WOW in ride comparison. Of course its not for the racers but its the pinnacle of fine comfy riders. You really wouldn't know of this unless actually experiencing on the same day. Immediate and huge difference. I'll get off my soapbox but its fun to talk to makers of tandems of that time. No way today could they afford to make such fine production steel tandems like those again. Nail the gearing down to help offset the handicap in climbs and you have fine rewarding tandem. For vintage 80's, shop for a deal on some better upper model Santana. You won't be disappointed.

Too much and wide topic for getting into here, but tandems are on whole different level of cycling. I don't blame others for not understanding why nor liking them but on the other side, can be some of the best experience and most fun. Whether the locomotive leading a paceline or thrilling hair raiser on fast descents, its at least worthwhile trying once and then make the call.