Here are some answers to adanac PM, I put them here, others may find this interesting.
1) Does the Naza or WKM not help with stability? My understanding was that it "assists" with some flight parameters.
Yes they do, GPS mode helps you fight the wind the MR stays where you put it.
Atti mode makes the MR hold altitude and when sticks are centered the MR is level, but it will drift with the wind. This can be used to advantage for filming, it is less jerky than GPS as GPS keeps correcting all the time. The Zenmuse will even out the jerkiness but lesser gimbals has a hard time with this and you need to use post stabilization in your video.
2) Was it the lightness of the F550 that made it susceptible to wind? Would a different gimbal make the difference?
Yes a lighter craft is more suseptible to turbulence. Smooth wind is not a problem, turbulence is, there is always turbulence around buildings trees hills etc when the wind is blowing. A heavier MR is not affected as much.
3) What do you reckon the payload of your F550 is?
Realistically maybe 1 lb after you add a battery, 1 1/2 is pushing it. The 550 is made for takeoff weight of 2.7KG, the S800 is made for slightly more than 7KG. Don't forget batteries are part of this and the batts for the 800 are very heavy more than 3 lbs, but this still leaves a much greater payload. The Zen is heavy.
Patrick at AerialMediaPros.com is a great guy to talk to about choices there are many. He has always answered all my questions and his recomendations have proven very good for me.
Check these videos, they show the 550 and 450 video with post stabilization:
https://vimeo.com/57225152
https://vimeo.com/57552088
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And just 450 with no stabilization, no gimbal:
https://vimeo.com/57337774
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Here is the Zen 800 raw footage:
https://vimeo.com/59617201