The Common Cents System is just that, common. Back in 1962, just as the AFTMA was coming out with the new method of line ratings (by weight, not diameter), the shops selling fly rods (not many were fly shops) had deflection charts in the back room so you could discern the standard deflection and the bend.

Some quotes:
"...buying a fly rod in the average city store, that is, joining it up and safely waggling it a bit, is much like seeing a woman's arm protruding from a car window: all one can readily be sure of is that the window is open."
from Anatomy of a Fisherman by Robert Traver (1964- McGraw-Hill)

"Again, let me remind you that rod action is an elusive and variable thing, refusing to be encompassed by exact definition. The mathematics involved are complex in the extreme, even in the theoretical stage, and its permutations make admissible only the loosest of generalities."
from "Field Book of Fresh-Water Angling" by John Alden Knight (1944- Putnam)
I must agree with the gentlemen above. My casting style (it's not so much a style as a hope) will differ from yours and my interpretation of what part of the rod is working will as well.

The CCS does not take into account the mass of the rod, especially the tip. With a bamboo rod of medium or slow action (or extreme parabolic) the mass of the tip makes a great contribution during short casts. In fact with some of the older wetfly rods, no arm movement was necessary to lay 20-30 feet of line down delicately, just a simple hand motion. If you don't appreciate the contribution of mass, read Schullery on the subject in New American Trout Fishing.

CSS also doesn't take into account the diameter of the line. You can cast a 4wt rod with a Phoenix DT silk, the try the same rod with a Cortland 555 (the white sausages). The rod handles completely differently.

More later. Thanks.