I'm no expert, but I am in a similar situation as you...1/4 acre triangular pond, 10 foot deep, & a Gast 0523 (just not in Florida).
I plan to use three diffusers. The pump will handle three just fine best I can tell, maybe 4 or 5. One will be placed in the 7 to 8 foot depth (hopefully this will secure a small thermocline for heat relief) and the other two in 4 foot depths about 75 feet apart. The one in the 7 - 8 foot depth should be all I need to turn the pond over 4 times a day. This leaves the other diffusers as bonus turnovers even though they are shallow. All the diffusers will be on flow control valves so they can be balanced or shut off if need be. I am leaning this way so that I can better disturb the surface. I have a fair amount of pollens and dust floating around and the pond will ice over a couple times during winter and having a diffuser close to shore will allow me to keep the ice open if need be.
According to Vertex's Lift Rate Chart, the lifting capacity of two separate diffusers is the same as two closely manifolded together.
If your looking for pure turnover rate for the dollar...manifold them
together. You'll save on line and plumbing.
If you have some extra money...spread them out for aesthetics.
No experience here...just lending my ideas.
