I learned the hard way not to mount a 2-stroke inverted.

When the motor is not running left over oil in the engine will run down into the glow plug. If its up right or sideways the oil pretty much collects in the case. To keep the oil from running into the head and plug you end up storing the plane inverted, starting it inverted on the flight line,....what a bother. The worst is when the plug does get loaded with oil and you have to remove it from the engine so you can burn the oil residue out. You have probably guessed by know that these poor plugs didnt last long either due to the abuse.

Because the plane I have requires the engine to be mounted inverted I had to go to a 4-stroke because the plug is inserted at an angle and doesnt get loaded with oil residue.

Other than that I have never had issues with how an engine is mounted.

Cheers.
James