Just wanted to report back on the duct fans.

I have few Avalons 1246's all on the same rack.  These machines are in the attic, in Texas, and today is a warm day, which I was waiting for to report back

On 1 machine I hooked up AC infinity's 10" Duct Fan and Filter box on the intake side and just the duct fan on the exhaust side.  Both fans at about 600 cfm (50% of their 1200CFM capability)

Comparing the identical machines side by side - the non ducted machines fans are running at about 70% (5200 RPM) , the ducted machine fan is running at 48%(3775 RPM).

Also the high pitch of the machine was silenced to low rumble.  With this POC done, will hook up 2 machines per duct fan and hopeful quieten my house more, while I plan to plan to sound proof the area more.