You can fly a scale prop.. If you choose not to, that's your choice. You could put an RCV 120 in your bearcat and probably fly a scale prop, or at least one that was closer to scale than the small 2 blade you are currently running. What you cannot do is put a scale prop on a normal model engine without some sort of reduction drive. The RCV is designed to turn the prop at 2:1 reduction. You could make your own reduction drive, in some cases purchase a commercial unit. Here are 2 pictures of my Ultra-rc Zero with a G62 and a Torquemaster 1.75:1 reduction drive with a scale prop.