comment about the Dursos.
I read as well that you should go up one size but my experience it's not required with the larger pipe size.
I'm running 2-2" threaded bulkhead with Dursos and they are both silent and I'm splitting probably 1000gph between them.
To make, just threaded a 2" TA into the bulkhead and built up from there staying with 2". The only mod I did was because of limited space in the overflow towers using 2", and since couldn't find a 2" street elbow, was to basically make one by cutting the 90 and Tee back before coupling.
