Another option:
If you buy a Ke Nalu, with the Extended Ergo "T" handle.... you have 10" of adjustment, but not on the fly.
All the componants of a Ke Nalu, are assembled with "Hot Glue"... so just a minute with a hair drier or heat gun, and the handle can be adjusted to length.
Not useful as a "guest" paddle, but great for being able to dial in your preference, on a world class paddle.
The Heat gun makes quick work of the adjustment.... apply heat, set the length you want and let cool for 5 minutes... good to go.