Hi Mike
Impressive system would be a major understatement for your labor of love
I found your system from a search on the Durand Talea II. Impressed you went to two Talos'. I just bought the Talea and await the arm. Replacing a solid Triplanar.
I notice your fabric treatment is over only small portions of the walls. How thick is it? How far do you offset it from the wall? I have sheer curtains on my windows behind my speakers.
I had some help putting diffusion panels behind my listening area which completely messed up my tonal balance - shrill top end.
Since you have a beautiful acoustic room and a topflight 1/2 inch reel to reel, have you considered buying or borrowing a set of studio mics and having a small string quartet etc record 2 channel direct to your R2R?