HERE IS A REALLY KEWL IDEA!
How about a 18650 twisty tube. This would strictly be a tube, perhaps with a mushroomed base allowing for tailstand. There might be sume knurling or other scallops on this end to assist in twisting and also for lanyard attachment. O rings of course.
The other end screws into the head. This would convert your U2 into a twisty with tailstand while shortening it up big time.
I wonder what it would look like sized for, say, a Pila 150S?
Advantage: Shorter, smaller, lighter, tailstand, 18650 or Pila capability.
Disadvantage: Lose clicky, not much else.
--------\
.............\.....................................===| <- FLARED BASE
...............===----------------------......|
U2 Head.........|.......18650 tube..............|
....................|....................................|
...............===----------------------......|
............../.....................................===
---------/
crude ascii drawing above