The current design, warts and all, is mostly my fault. The widest point is 8.5" with a Mag 7. A mag 9 will be more like 9.5.
Do you have one?
I don't recommend a Mag 9 for anything with a main reaction chamber under 4 feet tall. A mag 7 or even a 5 works great for our standard design which has a 30" tall reaction chamber.
I know I said Mag 9 after the last round but I figured out a better way to deal with the aspirating venturi vacuum problems that doesn't require the bigger pump.
I need two Mag 9s for a mod I'm doing on my tank. If you've already purchased a Mag 9 I'll buy it off you for what they cost on Marine Depot.