I'm interested in capturing 360-degree video using an S1000+ with an array similar to this but with Panasonic GH4s, and I want to minimize the amount of the frame that would show the S1000+ itself. Does anyone has experience with having the payload hang below the landing skids?
I envision attaching a 3-ft rod to the S1000+ with the camera array at the other end. I realize the takeoff would have to be modified in some way once the payload is attached — has anyone heard of this being done successfully?  

I use  50 mm lens that doesn't pick up anything when pointing horizontally after the landing gear come up.

If you're using smaller lenses, perhaps something on a servo controled arm that can swing down once the landing gear come up?
Another option might be an octagonal "ring" about the same diameter as the rotor motors when extended for flight. If you hang this ring from the lower deck that has the dampening rubber joints, and then mount the cameras at flat side of each ring face, the cameras would all be much farther from the center, so less likely to have any of the UAV in the frame. They would still be evenly distributed in weight, so the S1000+ wouldnt mind. You couldn't raise the landing gear any more, but you wouldn't need to because the cameras would all be outside of the gear.