Heya Wayne
Have you thought about using a Herbie instead of the Durso?
Much quieter and easier to adjust. You already have 2 holes for the drains and a third for your return, so I thought I'd throw it out there. You won't have to run your return over-the-top like so many of us. Plus, you may gain some clearance as Dursos tend to be tall.
I've been testing mine with freshwater for the last 2 weeks and am extremely happy with it.
Here's a link for you to look @ Delphinus' ... scroll down a bit for his pic of the standpipes.
http://www.canreef.com/vbulletin/sho...&postcount=244
My tank is a 19" 75g. I run my 1" drain about 4-1/2" from the overflow height and the emergency is @ max height to the lip of the overflow.
Both of those measurements include the 3/4" strainers pictured in Del's link.