My own TwinFire - No longer a hypothetical!

[perttime]

Also, using normal props isn't the end of the world either.

... I wonder if there are suitable 3D files of prop blades out there, for printing them.

[Wardukw]

I did a search for contra blades and dodo was the result..everything else is there in mulitable scales ..which surprised me to be honest and some of the prices for them made me glad i was sitting down.