I went ahead and bought the more robust mount from Servo City. The other one just wasn't going to be solid enough.
I've also shopped around for a good, and I mean very good, suction cup mount. I don't want it to add excessive vertical length to the mount for fear that the camera view will be limited to the instrument panel, and I don't want it falling off. I also has to be affordable - you can easily spend hundreds on these things.
I found this:
The picture makes it look gigantic, but consider that the stubby bolt protruding from the center is only 1/4" in diameter, so this picture is slightly above actual size. I will add at most one inch to the vertical measurement of the all-up mount and pan & tilt stuff.
I like it because it is pump activated, and the pump doubles as a suction indicator. If it is getting ready to drop, the red line becomes visible and you just pump it again. It reportedly can carry up to a 15 pound payload - whatever camera I end up mounting to it (it won't be the one I'm testing with) will weigh less than a pound, and the pan & tilt mechanism won't add a whole lot more. Even at two pounds combined, pulling six G's would rip the wings off of the airplane but this mount would still be within published specs.
It costs $47.50.
I went out to the hangar with just the pan & tilt to see what it looks like in its current state:
The servos are pretty jumpy, some of which is caused by my trying to hold the mount steady against the canopy, but the rest is electrical.
I also still have the problem of the centering springs on the joystick wanting to constantly return the camera to its center rest position. I'm thinking that I can address that by adding a switch the only applies power to the servos while a momentary switch is held down. That way I could position the camera where I want it, then just let go of the button, Tapping the button would re-center the camera.
Future versions could include a handful of 'memory' buttons that would store the current camera position and return the camera to the stored position when pressed. That experimentation I did a couple of years ago with the Arduino prototyping board would come in handy for that!
That seems pretty workable.