Pretty cool zeppelin !
I don't think you'll have any problem with the two 1" overflows and drainage.
If you do, or if you want an option, coming off the mag12, install a tee with 2 ball valves coming off the tee.
Connect the tee so the "straight-run-through" of the this tee is from pump to return line. This is where the bulk of the water will be going.
From this straight shot tee side valve - run your return plumbing to display..
From the other tee side valve - run a bypass back to the sump.
If you have too much flow, you can open the bypass valve and redirect some water back to an area of the sump.
You could also throttle back on the return line valve to increase or decrease flow up to the tank if necessary.
Either way - it's cheap and good back up plan.
Also - if you want to remove some water for water changes or whatever - you would now have this additional bypass line.
You can do all kinds of stuff once you have the bypass available.
A PVC union on the pump makes for easy removal and maintenance of the pump.
Just a thought
