I don't know. It would be interesting to build a bike with a number of pressure/tension gauges around the frame, and put it through its paces.

I presume the "Slingshot" bicycles are stable enough to have actually made it into general production (road and MTB versions), although I'm not sure what they're like to ride.

A little different concept, with a hinge at the toptube/seattube junction, and a simple cable for the downtube. But tension on the DT means compression on the TT.



Looking at a normal double triangle frame, the chainstays/seatstays would act as a large lever/pivot, essentially transmitting the entire rider weight onto the TT compression. And, it may not be easy to interrupt that compression pressure.

I can't say what I would do if I was "car-free", and riding that bike as primary transportation. As it is, I probably have an old steel frame that I could move my components over onto in an afternoon, and discard that frame. But I might consider trying to temporarily stabilize the joint while waiting for a replacement frame to arrive. And ride slowly and carefully.