Yes.

I usually go with 80% of the FSA. FSA is Fan Sweep Area, which is the O.D. of the impeller minus the diameter of the EDF center hub. So it is a doughnut shaped ring. Calculate that area, then you want the outlet diameter to be 100% of that diameter value for thrust, 90% for a mix of speed and thrust, or 80% for speed and less thrust. Once you go below 90% the amps will start to go up from back pressure. On my old Wattage MiG I did the calculations and found it to be exactly 100% which made sense as that was built around a brushed 400 motor using their 6-blade impeller for maximizing thrust using a weaker brushed motor. I set mine up with 4000Kv brushless motor and took 3 blades off the impeller because I was going for more top end speed (trading off a loss of thrust) but it still had plenty of power out of the shoot. I then did the exhaust nozzle duct mod reducing it down to 80%. I gained approx 8 mph with an increase of 3-4 amps.

As far as the inlet goes you want to shoot for 120% ideally from what I have been told. But that's not hard to do if you choose to perform that mod as well because the opening in front of the EDF unit is a complete round circle, not a ring like inside the EDF unit itself. You also want to radius the leading edges of inlets, no sharp inlets. I haven't bothered doing any inlet mods yet as the performance of the EDFs I have is either good as is (for me) or the exhaust duct mod to 80% has given it enough of a performance boost (again for me and my tastes).

Hope this helps.