The Dynavibe produced a different result for me and may have saved my butt. I was unable to obtain a stable reading with the device. The velocity (IPS) reading varied widely up to 2.3 IPS and the phase angle kept rotating forward. E-mail support from RPX Technologies (Dynavibe manufacturer) was excellent. They suggested something must be moving, maybe my spinner.
I removed prop and spinner to get the spinner backplate off and discovered that one of my IVO medium blades is cracked (see pic near upper right bolt). That explains the movement and why the Dynavibe wasn't giving good readings.
IVO says the blade is unrepairable so I have to send them the remaining good blade and check in order to get a matched pair back. I'm not happy at having to shell out some bucks, but am very happy to have found the issue while on the ground.
Dorsal's added me to the end of the summer tour list so I can balance everything once I'm properly propped again.
I think it's time for me to retire the UHS fiberglass spinner. The time it takes to remove and reinstall in order to re-torque the prop bolts at the IVO specified 10 hour intervals is just too inconvenient. Or maybe I should switch to a less maintenance intensive prop.