I always thought the best way to measure chainstays was to give the measurement as the intersection of stay and stay, until I started seeing some bikes that only shift, feel, perform best when put the axle to one extreme of the dropout or another. As has been said, when you don't standardize the chainstay measurement, you don't standardize wheelbase, bb drop either. I still don't get why seat tube measurements were never standardized... Some always quoting from center of bb to center of seat lug and some to top of the top tube. It seems there is never a reason to quote to the top of the top tube as for most bikes the top of the top tube doesn't go that far, as the seat lug either dips or climbs at that spot.
More disturbing is the way bike weights were and are calculated. I was surprised to see a Cycles Gitanes catalogue (mid 80's), that quoted the weight of their bikes using a 57 cm frame instead the more popular 54 or the lighter 51! Such a thing would never happen today as bike weights are quoted fancifully, weighing the lightest frame offered, without pedals and without bottle cage and with the lightest seat available. One local bike shop weighed the Specialized frame using a fish scale and hung it up for a display to catch possible sales to weight weenies. Even with the sub 200 gram saddle, and no pedals and weighing the frame designed for men of about 63 inches tall, the bike still weighed more than the quoted weight in the Specialized catalogue. Just try weighing the 54 with pedals and a normal seat that someone might enjoy, and you might find that these 16 pound wonders really weigh 18! Bravo .... three pounds under a classic bike and you get the durability of toilet paper and the comfort of a policeman's night stick in with the bargain.
Garth Libre in Miami Fl. USA