If you want complete coverage I would go with 2 mp60( 1 on each side) and 4 mp40 ( 1 every 2ft on the back wall) you could go with 4 mp60 on the back wall but you would have to dial it to low
I have a 96"x24"x24" and I use 2 mp60s on the ends and 1 mp40 in the middle. I really have to dial down the mp40. Since your tank is wider and higher. I think 2 mp40s on the back and 2 mp60s on the ends.