Plumbing

Ok, I have everything plumbed and set up on my new 162 gallon in wall tank. I am about to add the substrate. I am concerned about the water line. I have a sumo, so the water line only move up or down if I open or restrict the drain coming from the overflow. I attached the wall wood trim around the tank, filled nail holes, paint, etc, and whe I have the overflow drain fully open, the water line is about 1 inch below the trim. I have to back the drain off about 30% to get the return pump to raise ...

I am planning to use an Aqua-C EV-240 skimmer on my new 162 gal reef tank. I see that you can buy them with either a submersible pump or an external pump. If run with an external pump, does the skimmer then sit outside the sump?

Also, I would then need to runa separate external pump for the flow through the sump and fuge...correct. Do I factor in both pumps for total flow rate in tank?

I also hear of a lot of people running 2 return pumps, in case one goes bad, you have ...