So not vintage yet and debatable if it is classic or not but I had no idea they made MTBs too
Police Auctions Canada - Softride PowerCurve 21-Speed Bike (150515D)

If anyone here gets it - please ride and post your impressions

I used to have a Softride Powerwing for time trials, duathlons and triathlons. The problem with Softride beams for ATBs is that they provide no crotch clearance in emergency or forced dismount situations. In fact, the moment they are unweighted, they jump up to greet you. They are also top heavy bicycles, which isn't very desirable on technical trails.

That's hilarious, am I supposed to fully sit for the entire duration of the ride, instead of standing up on the pedals over bumps?

I guess it could be good for well groomed dirt trails.

"The problem"? Along the lines you've mentioned, they remind me of catapults with large wheels. While horizontal compliance is better for MTBs (as a bit of lateral compliance is arguably a benefit for road bikes), the top tube is not the place for it. A Softride would be about the last thing I'd want to be on a moment after the rear wheel came down hard.

Off topic but that auction site is one of those where each bid extends the auction end time. Really caught me by surprise - bid at the last moment and the end time jumps 10 min. You sit watching the price keep going up and up.

Its 25 years old. Thats pretty darn vintage for an mtb. The Allsop Frankenstem is a cool feature

I was tempted for a second or two, thinking of nice fat slicks and ride it on groomed trails or backroads

It is only happening if there are many close bids at the last minutes. On items with fewer bidders it does not do it and if you are far enough ahead - you'll get the item (no idea what are the actual metrics).

I had a Softride MTB frameset briefly but never built it up. Got the frame and fork from one guy and obtained the beam separately. I still have a couple of the stems.

You must be use to full-suspension, where you land with your butt on the saddle.
I've had my Norwester in the air a few times, and if you land it like the rigid that it is, the seat doesn't 'spring up' at you.

Don't look at it as a full-suspension bike, it's a rigid, with a well-suspended seat. Gotta remember, this is early-mid 1990's tech, where suspension was still developing, and the different builders were all trying to find the 'better mousetrap'

The beam bikes are definitely compromised for standover clearance, even the road bikes; getting on and off requires some planning ahead, and you loose the room to 'english' the bike in tight quarters.
They do climb like crazy, but you have to be very smooth. Mashing the pedals will give you the 'pogo stick' that people complained about.

They're also tricky to set up, since the TT length isn't fixed, and the seat height is dynamic. Once you get it dialed in, though, it is smooooth. Gravel tracks and fire roads feel like they're paved.

As MTB tech, it was a dead-end; the stem was (still is) the best of the designs, but due to the tech of the time, it's both heavy, and way too long to work with 'modern' frame geometries.

The problem with mounting and dismounting is that the saddle height is set about 2" higher than normal, to compensate for beam sag under the rider's weight. You have to swing your leg a lot higher to clear the saddle.
I recall coming into a triathlon transition zone and seeing several cyclists topple like dominoes, when a Softride owner swung his leg into the saddle, instead of over.