Help with diy external coast to coast overflow on acrylic tank

[Alazo1]

I have a 120 acrylic tank. (48x24x24). Tank will be in wall.
I recently removed the two corner overflows. I have a lot of gouges from the grinder but will skin the inside of the back and sides with 1/8" black acrylic sheets.

Wondering what you folks think of doing a total external overflow.
I was thinking of cutting a slit (straight line) across most of the back wall and making a box in the back.

Questions:
How far from the top should it be and how wide should it be?

I don't have a router but always wanted one. Any recommendations, also what bit?.

Is this doable?. I suppose if it doesn't work I'll be skinning with the black acrylic to cover it.

The first pic has a black line that signifies the cut.
The second pic is just so that you can see the butcher job I did to remove the overflows..LOL

 

[Alazo1]

I forgot to mention, this is 1/2" material

 

[burnetb1]

Someone with more experience with acrylic can probably chime in here and help more than me, but here are my thoughts:
-1/2 in. might be a little thin for acrylic if you cut into the back. Since you will be adding a overflow box to the back, maybe you can support the back wall so there is no flexing. This is also made easier since it will be in wall and you can hide any bracing.
-instead of one continuous cut for the overflow, make 2 or maybe 4 smaller cuts. You will still get the coast to coast benefits without making the back of your tank effectively "rimless". Since its thinner acrylic and have euro bracing I wouldn't make a single continuous cut across the back without serious bracing mentioned above.
-last thought, I hope you seal up those holes in the bottom real good. Holes/bulkheads at the bottom of tanks scare me...lol