Overflow dimensions

[WuHT]

i'm planning (have to submit drawings)a 150 gallon aquarium , and i'd like to know whether it's recommended that i have two overflow boxes on each corner or just one (my current stand will be better off with just one).

If i were to have one overflow, what would be the best dimensions for the overflow if i were to run the return as well as a durso standpipe ?
3" by 9" ? 4" x 8" (the overflow calculator on reefcentral says that i need 9inch linear overflow length for 600gph..but i dont know if that value includes the teeth or just the gaps)

I'm most likely running a 1 inch bulkheads (so 600gph) as my drain, and for my return i'd need a 3/4" bulkhead ..so taht means my largest drilled hole should be 1 3/4" inch ?

Help please, and thanks in advance. -- I asked 3 times on reefcentral, and my threads get buried in no time! Might as well try here as well!