People, well bike journos, are always banging on about the importance of lateral stiffness and a rigid bottom bracket, for efficient power transfer, but is it?
Van Nicholas had Delft Technical University test the stiffness of their bikes and what they found was that their was no real loss of power whether the rear stays flexed or not - what there was was a difference in the immediacy of the power delivery.
So, big lad sprinters need everything to be stiff and immediate - in power delivery terms at least (hence the extra stiffening give to the chainstays their new Astraeus, while tourers and commuters might be better off with the smoother delivery you get from a slightly less stiff set up…
Basic physics innit, you put power into something to bend it in one direction it is going to return the same amount of power when it flexes back in the opposite direction. You can't really 'lose' power anyway. Okay, pedants can quibble that a tiny amount of that power will be dissipated as heat and even noise but we're talking infinitesimally small amounts.
Makes you think… which is generally a good thing