are you talking abotu two different glow motors or are you talking about two counter rotating propellers on one crankshaft? if you are talking about having them on a single crankshaft, you will not be able to use a two stroke motor because you need to run a second drive shaft through the crankshaft that you can attatch the second prop to, and the two shafts are tied together with a gearbox. if you are talking fourstroke, that is a lot of weight and will require re-balancing of the shaft and an out of balance prop could mbend the shafts. if you are talking about two seperate glow motors, you may find that the two are not identical and produce slightly different amounts of thrust for the same amount of throttle. i think one motor and other electrics around the sides countering it are the way to go