Well all the engineering stuff here passes over this history major's head with a "whoosh"!
But if 753 is that thin "in the middle" of a double-butted tube, I would think it would FLEX more than other tubing. And judging just from the ride of my '80 Raleigh Team Pro, it's anything but stiff even with true racing geometry. It's hard to define the feeling (too much of a guilty pleasure perhaps!) but it feels wonderfully resilient if that's the word. Simple fabulous riding machine.
But it ain't stiff.
Peter Kohler
Washington DC USA