Yeah, that sounds like a well developed clunking if you can feel it when riding.
There have been a couple of driveshaft failures on these bikes, one was catastrophic and the cause was not determined if I remember right (it spit parts out on the highway so hard to diagnose) and the other caused a ripped bellows due to the C- clip slipping out from the trunion. There has also been at least one bevel drive bearing failure that I know of and it would probably be impossible to find that problem vs. a driveshaft noise until the parts were broken down and inspected. Any significant shock to the driveline will radiate noise and vibration everywhere (in the drive train) so it would be hard to locate the source.
The normal 'tinking' noise in C-14s has been due to the front spline on the driveshaft being dry. Grease in the splines just deadens the impact of the splines as they shift from side to side so the noise disappears but it does not really cure any problem because there was no problem to begin with.
By the way, I am not making fun of your drive train clunk, just the occasional herd reaction to reports of <mostly> phantom problems. You know this or you would not have posted using the title that you did. :-) What is really comical is that some folks pick up on things like reports of driveshafts making a tinking noise and go on to report that they too have the 'common' or 'well known' driveshaft problem.
Brian
@ B.D.F.: I realize that the suspension is unloaded and doesn't give a completely accurate representation of what is happening while I am riding. But, it is the exact same clunking sound that I am hearing (and feeling) while I ride. The biggest thing may be the location along the driveshaft where the clunk is happening. I will be calling the dealer in an hour or so but until then I will probably pull the cover and do a little investigating before I leave.
