+1
So if you can get a 16ga on a 20ga frame safely was it really a 20ga frame to begin with?
IMHO, "scale frame" has been left seriously undefined. Does it mean a size smaller than the next larger gauge (12 on a 16)? Does it mean the smallest frame a given gauge can be built on? Or, does it just mean the size a gauge is usually built on? 20 ga frame is not exactly one single thing.
As above, which size 20 ga frame are we talking about? Way too much has been made of the idea of 16 ga on 20 ga frame. If you can build a 16 ga on any given frame, is it not a 16 ga frame? No doubt that you can build a 20 ga frame that would be unsafe for building a 16 ga on. Why no hue and cry to build 20's on 28 ga frame of 28's on ,410 frames?
Sub 6 1/4# guns quickly become difficult to handle for most/many shooters. 12 ga guns have been built down into the mid 5# range with 2" chambers.
Thus endeth the rant.
DDA