RE: K&B 6.5 FIRE / SCREAMIN' DEMON
The DF engines scare most buyers because they aren't sure about adaptability to prop planes and there sure is no way I'd buy one that is used! If you could build fast enough to make it profitable, RTF Demons with engine combos might attract certain types of flyers. I bought a 3D profile from Morris Hobbies a similar way...kit+engine.