I originally built my quadcopter using someone else's plans. It flew well, but I quickly found that it "needed" additional equipment (camera gimbal, GoPro, longer landing legs, FPV transmitter, etc.). These add-ons seem to have pushed the aircraft past its optimization point and eCalc estimates my hover throttle at 85% and flight time with a 3S/2200mAh battery to be 3.4 minutes for the aircraft's current weight (the flight time seems to be spot on, I need to test out the hover throttle). I'm in the process of trying to shed weight from the aircraft and am even considering going with larger motors. Unfortunately, I'm a bit confused about how to spec motors for this thing.
My question for you guys is, how do YOU go about designing a multicopter? Do you use a proven setup and slap an APM on it? Poke and prod at eCalc until it spits out something reasonable? Have a better understanding of motor specs and the thrust capabilities than I'm familiar with?
I'm particularly concerned about how you approach selecting a specific motor/prop combo for your aircraft.