Agreed that the diameter/wall thickness ratio, before beer canning is problematic, is a factor in how large a diameter a steel tube can get. Our demand for less weight and greater stiffness impacts the choice of steel by the masses. Some of us understand that a stiffer bike is not a better bike if carried out to the extreme. I don't think any race or ride was lost because of a too flexible bike (that was otherwise well designed).

I decided to not mention the diameter/wall factor to minimize the distractions from the basic material characteristics. Andy.