Extremely helpful, Steve, thank you!
Now that I know what the tech will do, my input is cemented.
I've read all about "toilet bowling" and I believe I'm caught in the flush. I live near Boston MA and found -14* is the declination setting, thus, 14* to the left is required. I adjusted as best I could, but I don't know quite how to best do so accurately. What do folks do who make declination adjustments? Trial and error?
Hmmm, I would go back a couple of steps in your setup as the root cause of your toilet bowl effect and you 'twitchy' hover whilst in ground effect could be the same thing. I would double check that the centre of your Naza is exactly on the C of G of your F550 complete with flight battery installed. From experience it seems that a bad C of G tends to exaggerate problems you experience during the more gentle flight manouevirs, such as take-off and landing, and even just hovering when you're well out of ground effect. So, double check your C of G and make sure that wherever the C of G is then that's where the centre of your Naza should be.
Also, make sure there is no excessive vibration - quick fixes to that include switching straight to the DJI 10" props are they require a slightly slower RPM over the 8" props, plus they seem to be better balanced and aren't quite as stiff as the 8" ones and therefore a little more forgiving to minor imbalance. I found you definitely get less vibes with the 10" props, even before you do anything else like balancing, etc. Vibrations really confuse the flight controllers. Also, you can find that whilst you might have very little and indeed acceptable levels of vibration coming your airframe, additional items (such as additional landing gear, etc) can amplify the minor vibes back into something huge again. Make sure that whatever you've got bolted to your airframe is as close to the centre of the airframe as you can get it, to avoid minor vibes getting amplified. You shouldn't have much of a problem with the F550 but with the F450 I've seen people bolt the frame for their landing skids onto the furthest end of the extended parts of the bottom plate and end up with massive vibrations which just don't exist when the skids are removed. It's been remedied by sliding the mounting points right up to the other end, toward the center of the F450 bottom plate.
You'll find that if your C of G is off then you won't notice it so much if you're taking off in a fairly abrupt manner, or in fast forward flight, etc. That type of flying tends to mask the problem, but when you have your thumbs off sticks then it will begin to slowly circle around in the hover and progressively get faster and faster. You shouldn't need to 'pop' your F550 off the gound too quickly - yes you should employ a degree of authority on your control inputs, don't try and inch your off the deck, but you should be able to lift into a hover in a nice and smooth and controlled fashion. You shouldn't need to yank it into the air at all. Yes, multirotors experience ground effect in the same way as a regular heli, but the flight computer should be dealing with that and you shouldn't notice it too much. If ground effect is having a marked impact on the stability then I'd definitely check that C of G, your GPS mounting offset, and your compass calibration.
Even in Atti mode you should be able to leave it in the hover with thumbs of sticks and the only thing that should require you to add any control inputs will be the prevailing wind. That's all. It should be able to maintain and nice and level attitude, as the name of the mode implies. You shouldn't find the need to continually put in control inputs to keep it in one place aside from correcting the direction that your model wants to drift downwind. If you're finding that it's a real effort to maintain your position, even on a fairly windy day, my money is that it's either incorrect C of G, compass calibration, or maybe you've not got the offset for your GPS sensor quite right. Double check you have set the GPS sensor off-set in the correct axis and that you've not transposed the plus and minus figures. Double check it and then triple check it to make sure it's as close as you can get it.
My money is on your C of G being out. Lets us know how you get on.
