[RAF_Magpie]

This is probably so glaringly obvious, so much so that its probably one of the first things you tried...

But: have you tried simply using "two engines"...? So as far as the game knows, its got two engines, one turns one way, one the other (like Fisneaky suggested, the P-38...)...

I'm sure, if that works, that people wouldnt mind having to toggle two engines...