If you're talking about the airplane getting fuel residue all over it, then that's another thing. THAT would also be considered completely normal. That's because there's a lot of oil being thrown out of the exhaust port of the muffler. The airflow around the airplane then takes over. You can try adding a tube to route the exhaust farther away from the airframe, but this may also add enough back pressure that the engine will slowly overheat. You can't tell if that will happen until you actually try it.

For years, it's been considered normal to have to wipe off the residue from the airplane. I've had models where you had a large, dark coating of fuel residue all down one side of the model. You'd have to use a few paper towels to wipe it off before you could use the cleaner to get the rest off, it was that thick!

As long as we run glow engines, we'll have fuel residue getting all over the model. Completely normal.