your byron fan and rossi 81 is a good poiwerplant for your app. do you have a thrust tube?? you must have a thrust tube on a fan to get your 10-12 pounds of thrust i've seen a byron f-15 weighing 32 pounds fly beautifully off a pair of rossi 81's my byron mig-15 weighs 14 pounds with all the bells and whistles and i fly with a rossi 81 its slow on the ground but it flys good onces its in the air as to the rossi 105 i've seen a lot of the 105's and heard all the pilots cursing at them also. unless rossi changed the carb set-up the carbs are not reliable from what i've heard from other 105 owners good luck donniercjet