Hello Big Bass Hunter. Your specs are close to an aeration system made by Vertex Water Features that I install regularly. It uses a 1/4 hp gast carbon vein compressor that produces 3.6 CFM @ 10p.s.i.(very close to your output)and runs two flexible membrane diffusers.
When I spec. a system I simply aim for 1 complete turnover per 24 hours. If your pond is 1 acre with a mean depth of 4 feet that's 4 acre-ft. That's 43560 cubic feet of water per acre-ft times 4= 174240 cubic feet with approx. 7.5 gallons per cubic ft or 1306800 gallons in the pond. Assuming you can place one diffuser more or less centrally in 6ft of water you can expect it to circulate about 2700 gpm. 1306800/2700=484 minutes to move the whole pond. That's only 8 hours to turn the pond over, so that's good.
One diffuser should be able to do it, at least if it was one basin. Now since the pond is "L" shaped it may really be more or less two connected basins with a shallower area in between. If that's the case, since your pump will likely handle it, you might as well go ahead and drop two diffusers in there, one in each tier of the L. Otherwise, one placed centrally should work just fine. I have been pretty happy with the Vertex Coactive Membrane diffusers. They are zero maintenance and have a five-year warranty. There are more efficient ones out there, but they are more expensive and you really don't need it for your pond.
A good rule of thumb for summer start-ups is one hour the first day and double running time each day thereafter. I have gotten away with starting up all at once in some new ponds where no sulfide smell could be detected, even right over the diffuser, but wouldn't recommend it. I hope this helps you keep your bass happy!
