Help. Coast to Coast overflow on corner tank

[Gahngoo]

Hi all. I've read a ton of info on coast to coast overflows. The tank I plan to have built will be an acrylic corner tank with two 36" sides (the wall sides that meet at a 90 degree). I plan to have an internal overflow box in the back corner with a bean animal drain. Dual coast to coast dumping into the internal overflow box. Picture attached for reference.

I want the coast to coast to be as minimal at possible. I'm not too worried about the lengths, but I would like to be about 1-2" depth and 3-4" height on them.

My questions are: How small can I make the coast to coast and still be effective? Do they each need to be 36" long? Any other suggestions?

 

[mcgyvr]

The proper answer involves too much math for me to want to do at this moment (or any for that matter)...

In general the longer the better but I would ballpark that you want at least 50% of the length to be effective..
I'm currently running a 24" overflow on a 48" tank and don't have any problems with a visual surface slick but I'm also pushing some "decent" surface turbulence with the powerheads and return outlets..