Well ... here we go!!!
This is one debate that could go all night. Aperature ... aperture...aperture.
Not for me though. Mick asked us to put forward our suggestions for an optimum photographic scope.
Do I need to be told aperture rules?
NO
If it's a debate about aperture size, count me out. That's too much of a ***** contest for me.
I like the path Bird is heading down though vis-a-vis size and portability. If that's an important consideration, and it is for most of us, then you'll have to trade off some inches.
14" IMO would be the upper limit? Even that's getting beyond most people for moving around.