I think you have enough flow for your tank right now. If anything, maybe something small in the sides. Can the “dry” side of Gyres be mounted inside of the overflow and be constantly wet?Trying to understand if more flow is recommended in every case. I have a young cube setup in October. Basically it's a 90 gallon with t5/radion setup. 2 returns sun by a sicce 3.5 and 2 mp40 on back of both sides mostly in antisynch. My question would be should I add another flow creator on the overflow like a gyre or just leave alone?
I’m with you. I have a 120 and most my powerheads on the back wall. It’s so much cleaner looking, but not necessarily the best flow.
I'm trying not to lose the ability to view from the sides.
As my frags became colonies and grew into the stream the Gyre's create, I now have a problem where the flow is causing the flesh to deteriorate and die on some corals. I've toned it back quite a bit and haven't noticed any changes, with the added benefit that I can keep goniopora and acans now. 
I think it's unfortunately a pretty subjective decision. I think most of us just watch our corals and let the tank tell us.
Still no where near the volumes moved on the reef. The magic triangle: water quality, water movement, light quality. Strong movement as opposed to 'flows is highly beneficial. Keep in mind that like light, different corals have different needs.
