Thanks for your note.
Interestingly, regarding the Synology unless SMB1 is enabled Roon is unable to view the directories. I am mounting directly from the app (I have not tried mounting outside of the app.)
Network usage on NAS when streaming over Ethernet is around 300k with a 96 recording. When attempting to stream same file over wifi the other Pi usually dies quickly. (Just because, I rebuilt that Pi using DietPi this evening to see if that impacted performance.) A Sonos Connect physically situated nearby (plugged into the same Bel Canto) plays fine (but down samples of course). As reference, 2g file transfers from W10 Surface3 are in the 4-6MB/s range, physically near the same wifi endpoint.
I don’t really know where to look for jumbo frames — the switch is unmanaged (mostly because years ago I couldn’t get multi cast right for Sonos at the time, and a generic switch “just worked”). Edit: I just edited the MTU on the Synology manually to 1500, and I’ll see how that goes.
Thanks for the suggestions.
Nathan