I acquired my first 20ga of my own in 1956 & to the best of my recollection have never been without one or more since. My favorite load for the 20ga in all these years since has been a 2DE-1oz load of appropriate shot size for the quarry.
This load has always given me most excellent performance in spite of all the disadvantages of the smaller bore, a length to diameter ratio of about 1.57:1 "Out of Square" for the 20ga bore of .615". Once many years ago when I was still doing a good bit of Squirrel hunting with a shotgun (later I switched almost exclusively to a .22LR for squirrel) I loaded some 20ga 1 1/8oz loads of US #5 shot. This gave a ratio of about 1.77:1. It also proved to be the most effective loads I ever used for squirrel in a 20ga (never used the 3" load of 1oz).
I do truly believe the necessity of a load being "Square" is extremely Over-Rated. If one shoos a small bore you definitely do not want to restrict yourself to that square load.
