hi bill
i took the liberty of making you a drawing.
in this design i went with a semi coast to coast overflow , by doing so it allows both of your returns to be tee'd off and ran on either side of the overflow box and will be hidden by the acrylic back panel, a slip x threaded bulkhead is then used with loc-line and flow dispurser.
i did it as a bean animal with 2 x 1 1/2" drains and a 2" emergency drain
both returns are 1" and a valve(union BV preferably) on both returns are used to control flow.
this design allows you to access your ball valves from the back of the display without having to reach in your box , it also allows the maximum volume to aqua scape with.
by doing a bean animal you allow yourself a bit less tuning of the herbies gate , but in turn will cost a bit more in plumbing as you are adding an extra drain.
1 is a full syphon, 2 is a trickle or so and the emergency stays dry untill its ever needed(god forbid)
here some jpegs i made i can adjust anything you like if you just tell me what you would like to change and the dimensions you would prefer.
sorry for the delay buddy and hope you dont mind me poisting this public to help with design.
60 x 30 x 36h
19mm all around
