I'm thinking about converting a plane to have retracts, but I think the wheels would be way to close to the CG, so I got thinking.
I know this would take some design work, but...
What about mounting a weight on some type of track/slider, attached to a servo. So that when landing or taking off you could move the CG back a little with say the flap knob on the Tx. Then once up in the air, move the CG up to the regular position.
Might also be fun on a 3D plane.

I don't know, maybe the weight needed would be too much.