[mark]

Running 2-2" drains and then 1.5" for the return from my Barracuda to bottom of display.

The 2-2" are lots but thinking moving to a Herbie so would be only using 1 drain but still have lots to play with. Reason thinking Herbie is though upstairs is quiet with the twin Dursos, can really heard the gurgling in the drains lines (no air with a Herbie, no noise).

I used a combination of flex and rigid PVC on the lines partly as easier for routing but on the return line I used the flex to give me large radius sweeps to get away from the loss with a sharp 90° coupler.