Right, I've cut a piece of 3mm Lexan to fit, you can see in the pictures just how un-level the base is, but that's what I have to work with, so that's what I've got.
The OtterBox will be attached to the Lexan sheet (not sure how yet, I'll worry about that when I get there) I'm going to drill half a dozen holes through the Lexan and into the base, apply a good layer of silicone sealant, then screw the whole lot together. With firmly crossed fingers, a dose of luck and a following wind, it might stick.
Now...ballast. The swan I looked at in the video I posted doesn't appear to have any ballast, or none that I can see, so that's another ''worry about it when I get there'' job.
The reason for all this...I'm trying my hardest to avoid cutting into the bird, I've done a couple of ducks which I've cut into the backs, and the resulting joins have always looked awful, they never fit any sense again, hence the fitting of the watertight box underneath.
Oh, and fear not...I'll not be using 2.4gHz radio, I have a Graupner 40mHz radio which was earmarked for my Robbe U-47, I'll be using that.
Rich