I've heard it is best to store Airplanes [engines] with crankshaft facing upwards. reason is said to be protecting the crancshaft ball races from corrosion and gumming oil.

I think it makes a lot of sense from a technical pow, however, if you store a model only for a couple of weeks it wouldn't make a huge difference.

Nowdays, I always end the flying day by stopping the engine by disconnecting the fuel line from the carburetor, then I spray a lot of WD-40 in the carburetor and glow-plug hole or exhaust port, then I flip it over some 10 turns.

To protect the airplane itself, hanging it so it "sits" on the wall, with nose facing upwards, is my favourite method.

Hanging the models in the ceiling is nice too, looks great !

Cheers,
Ikaros