question about external overflows on a 380

[reefpatrol3]

I bought a used tank that is 120" x 25" x 31" (L x W x H ) made from acrylic, the problem is it doesnt have any overflows. It just had six 1" holes drilled in different location in the back panel. What I was thinking is is to put two external overflows, one on each end. I made them but was wondering about the teeth for the overflows. Instead of making individual teeth on the existing tank ends can I just cut out a slot like a weir overflow? Something like a 1" x 22" slot cut out about an inch from the top. I dont really want to do anything on the back except maybe use the existing holes for a closed loop.
the external boxes I made are 23" x 9" x 22" , made from cell cast acrylic and will be attached to the original tank with weldon.

unless anyone else has any better suggestion

 

[AQUA DAVE]

yes you can cut a single piece out then if you needed you can put another piece of acrylic with teeth behind the straight line you cut. or top the part you cut with eggcrate or something similar.