I’m unclear how Jones does that, as those frames look quite triangulated and braced. I can see how the Jones seat tube could bend backwards and forwards.
There’s a lot of flex in the post + ST area when seated but stood up the whole frame seems to work as a sort of leaf spring. You can feel it when landing, ride a diamond frame off the same stuff and it feels quite different. It makes sense when looking at it side on, remembering how rigid the fork is and not thinking of flex as coming from just the rear triangle (not meant as egg sucking as I know you’d recognise that a lot of frame flex/comfort that is perceived as ‘rear compliance’ is front end give).
But if you put a 12PSI 650×3.3″ tyre in the back of a space frame I’m not sure if there would be much frame flex, as far as I understand it’s why Jeff doesn’t sell a fat space frame, although there’s pics of one he did make ages ago somewhere.
(you all knew I couldn’t not chip in on the Jones aspect eh)
I can see how this idea could work differently, more seated flex, if the rear end’s not affected too much by not attaching stays and ST. May as well try it. I cut a 1″ section out of an old hardtails stays once to see how it flexed, and rode- briefly..