Hey Benjamin, we're over in the Middle East and running an AD8/200/360, can you elaborate a bit more on the stretch?? You mentioned longer carbon legs, can you share any additional details?? Thanks in advance for any help you're willing to share!
Personally, I think you are planning to carry an FS700 with the wrong airframe, never mind the camera mount.
The standard AD-8 HLE, with 410mm booms and 12" props, was touted (on the official Droidworx spec sheet) to be a suitable platform for the Canon 5D. That equates to approximately 1.7kg with lens. Having purchased an AD-8 HLE on the strength of those recommendations I subsequently decided that it was operating too close to its safe limits with that payload and 'downgraded' the camera to a GH2. Happily, the GH2 delivers better results anyway so nothing much has been lost.
However, in the meantime Droidworx have changed their position somewhat and now say the AD-8 is not really suitable for carrying a 5D and instead recommend the NEX or GH2 as suitable cameras.
The FS700 weighs in at pretty close to 3kg with a decent lens. Add that to the 1300-1400g of the AV200/360 and you are way outside the AD-8 comfort zone. It will get off the ground but that is about all you can expect. Ask it to do more and you had better get some hefty insurance organised. If you really want to carry an FS700 you need a much bigger airframe.
Start with eight 14-15" props and work backwards.