I guess I forgot to provide the update for my completed project.  

I did manage to successfully extend the yak paddle about 8 inches.  So, its not quite a 9 footer.  The paddle now has an extra thin-walled stainless steel tube in the middle.  It has a quick-release detent button on each end of the tube that secures it to the former mid-paddle connections.  Going this route I can use the exiting holes to provide a light angle to the paddle face (but I doubt I'll need to do this).  This solution also permits me to completely remove the extension and go back to the original configuration if ever needed.

The extension did produce a minor problem on my 10-mile test drive.  With the extra length, my hands no longer naturally fall on the hand grips that are on the paddle.  This is not so much a function problem as a "comfort" issue.  First, after a day's paddle the aluminum oxidation on my hands was clearly obvious.  Secondly, gripping metal in cold weather would not necessarily be pleasant.  However, I found a quick and cheap solution.  I found a rubberized grip tube for tennis rackets at Wally World.  I bought a pair and installed them in just a couple of minutes.  Now I have grippy spots for my hands plus a little padding should I whack something unexpectedly.

I did feel that I was "chili dipping" as I paddled along.  But I guess the more rapid stroke rate makes up for my deeper digging action with a bent shaft.  Oh, and I did find another benefit.  With the extra length of a kayak paddle, it is a much more simple task to push obstructions out of the way.

Fun little project ... something to keep the brain cells active.

dd