Update:
First some gratuitous photos
I got the sump/refuge all worked out. I had a Proflex Model 2 sump on my old 75 and loved how quiet it was. I even had built an add-on refuge that received water from my manifold, which you can see below that also was carried over into the new tank, and had a bulkhead that drained back into the Proflex. The problem with the add-on refuge was it was tallish at 18 inches which in the new stand wouldn't gove very much clearance to mount a light and it was smallish at only about 7.5 gallons.
A great local reefer was selling a really nice frag tank that was scratched up on the front real cheap which was perfect for my under tank application:
The height is only about 10" which was great for me but this presented a problem with getting the water back into the sump which at its lowest point is about 14". After asking around here on RC I got some advice to use a Uniseal which was simple and easy to use by drilling a hole in the Proflex and mounting it back to back with the rear 1" PVC drain that comes right off the back of the frag tank. I did need to raise the frag tank up about 3.5" so it's top is fractionally higher than the sump so in a power outage the frag tank wouldn't overflow. What I did was to use some left-over 3/4" sheet pvc to build a little stand:
Here you can see the sump back-to-back with the frag tank followed by a blurry photo of the uniseal on the sump interfacing with the bulkhead on the frag tank:
Some more of the sump and refuge:
Also here is the carryover manifold which will supply the main return to the Sea Swirl, BP reactor, GFO reactor and the flow to the refuge:
Here is the sump with easy access to the skimmer:
I also retrofitted the sump with uniseals on the drain line and added one for the Herbie style emergency drain:
I placed the gate valve knob out back of the stand so I can adjust it w/o removing the side panel of the stand to make it super convenient, you can see the knob sticking out a bit from a top-down shot:
I found that the AGA overflow kit actually make a nice adjustable Herbie standpipe with intake guard if you toss the durso elbow and just mount it straight up:
Finally the Sea Swirl was mounted on the back corner of the tank:
It does a nice job sweeping to cover most of the tank. I think with the MP40wES on the back and the SS it might be enough as I get a fantastic gyre flow around the rockwork with these two devices alone: