Results are in…
The C10r was subjected to 8 -10 hours of 60 hz at about 1/3 power (8.1v) and the output at that point had increased by something like 8db measured at the face of the speaker. This was done with the bare speaker sitting cone up on my bench.
I did not start with a virgin speaker as it already had a few hours on it and I had removed most of the doping before I thought to measure it. I used a Radio Shack meter set into a wood strip placed across the face of the speaker.
I think I got about 6db increase out of the C8r but the measurement was not as clean or complete.
There is now quite noticeable increase in the bottom and a smoother and cleaner top end. This is apparent with a guitar or playing music through the amp. It may be louder over all as the amp appears to have a bit more head room. I did not measure at any other frequencies.
All in all a very successful undertaking. Thanks for the suggestions.