For whatever reason, this reminds me of the time I lined up a 14' for 8/9 two handed spey rod with a DT3F line and fished size 16 dry flies with it. Kind of like swinging a buggy whip. Caught a half dozen or so 6-8" bows and brookies in short order, then put the reel on my 3 wt rod and had some fun.

I think the test might be, Bob, how light a 12' line / leader with a small fly can you cast comfortably and accurately for a sustained period of time ??

A Tenkara 13' Ayu will cast 20' of WF5F running line plus 12-15' of leader and tippet with a size 8 hopper with a bit of effort. But it will also cast a 12-15' furled line / leader with tippet and a small fly accurately and effortlessly for hours on end. The furled line / leader is roughly equivalent ( my best guess ) to a 9' 2X leader tipped progressively down to 5X.

John