Last evening, I took the Owens-Corning 703 panels from the back walls and added them to the ones already on the side walls which covered almost all the wood paneling down the side. That helped. The room now sounds noticeably more damped and the brightness, attenuated but not gone.

I also orderd another 6 pac of 703 from ATS Acoustics, 1" thick this time which I will lay flat across wire or perhaps mono-filament just below the ceiling.

As for the Cherry:

Finished up the walnut armboard and mounted the tonearm this AM. It sounds great! Can't hear much difference between the 29 gram Cherry and and my 5.5 gram SME III. Had a little more to say at Audiocircle

Now I can interchange cartridges in minutes by switching armboards and not having to do any adjustments.