Need help tweaking plumbing

[stgla]

Just finishing off the plumbing plan, need some advice before I buy all the parts:

The setup:
- 75g display
- 6x6x6 internal overflow box
- 1.5" drain drilled on the upper side of the tank, home-made durso, all 1.5" plumbing
- 30g high sump (usual glass tank w/3 chambers, homemade baffles)
- 5' vertical rise from sump floor to just over the top of tank, plus 2' horizontal, a 45 elbow, 2-90 elbows

I am thinking of doing:
- Eheim 1262 submersed for the return w/1" plumbing
- Seios in tank for flow (2x620?), to be replaced by a hangon closed loop one day in the future


Questions:

Did I pick the right pump? I'm turning down amazing deals on used Mag 9 and used Quiet One 4000 to buy a new Eheim, so say something now, please.

Should I throw away or sell my 1/2" SCWD?

I had another question, can't remember it...

[stgla]

Ok, now I remember my other question.

Should I mount the internal overflow box in the corner or off the corner?

The hole is already drilled in the side wall (the ugly non-viewing side), but I can position the overflow box so that it sits in the top back corner or 3" in on the side.

Advantages to off-corner:
- 18 linear inches instead of 12, so thinner layer of water sent to skimmer
- greater capacity for draining (limited only by return pump)

Disadvantages:
- possible dead spot
- slightly less efficient use of space in tank
- slightly less pleasing aesthetically

I'm leaning toward going off center. It's hard to pass up the extra 6 inches of weir. I have to drill the box this weekend but this is one of those decisions that I'd feel more confident making with RC posters' blessing.