My vote for cost savings, and effecient use of space two overflows in corners will take up less room than 1 big one..:yes:
3 holes in back ...3 bulkheads (for C/L)
2 overflows with 1 hole and 1 bulkhead each..for drain to sump
We go OTT with 2 C/L returns and 1 S/F return ...no holes, no bulkheads..
Plastic trim, and 1 cross brace in center...
If that works for you we can do "detailed" drawings (once) just about the time we hit page 11...