RE:>>>Caterham: ..."with "standard" tube diameters, lateral stability in locating the headtube/steerer was too compromised. oversized top & downtubes created a much more stable steering geometry which could be exploited without serious compromise."<<<

i earlier pointed out one of the compact design's major effects as being to significantly stiffen the rear triangle by the shortening of the seatstays & thus creating a very rigid pyramidal structure with the seatpost as its leading "leg" and the main triangle extended forward from the seatube.
using the earlier 25mmTT/28mm DT tubing "standard" in a compact design, the main triangle would be much less resistant to sideloading & twisting than the heavy braced rear triangle,calling into play my premise that the ideal frame should exhibit a smooth, even deflection over it's entire length to minimize the "hinging effect" with detrimental effects to steering geometry,stability and cornering. modern oversized and shaped tubesets increase the TT & DT's resistance to lateral and torsional loads and will reduce the disparity of deflection between the compact's main triangle and that of the rear.