W W Greener gave the 96:1 ratio of gun to shot wt at least as early as his 9th edition (1910). Burrard gave a recommendation based on FPS of recoil velocity, irregardless of gun wt. His recommendation will work out very close to the 96:1 ratio. Note that both of these were recommended for driven bird shooting (high volume) & for loads having a "True MV" (most vel listed my US makers is instrumental, not true MV) of around 1300 FPS.
In the overall scheme of things, personally I would consider any 12ga, except the miniature 2" guns, 6 3/4 lbs or less as falling in the light wt class.
