Looking for 180g less than 12" narrow box overflow

[servus]

Just got a 180g from glasscages. Due to the position of the tank in the room, I am restricted to a 12" width on the back for overflow and returns.

Overflow:
-> looking to use internal overflow, minimal footprint, what would you advise?

• The 12" Prodigy and Eclipse don't do more than 1000gph
• the Fiji LoPro that does 1600 is 18" wide.
• the H2O has a box that's also 18" wide; unless I use H2O without the box, then I only need room for the bulkheads... BUT IS IT QUIET?!?!

Returns:
- planning on bringing them all the way to the canopy, and coming down from there, without any holes in the tank

 

[servus]

• The 12" Prodigy and Eclipse don't do more than 1000gph

I am using 1" pipe for returns. Based on my math, each 1" pipe will do more than 1000gph. Why are these two overflows rated to only 1000gph, since the number and size of the holes seem to indicate more than that? Is the flow limited by the weir?

 

[servus]

Any thoughts?