Really... If you want to follow the recipie then just stick a 2.cycle .61 on there and be done with it. Otherwise if your going electric then making it preform in a similar manor to the original is all that makes sense. An 11x7 at 15000 rpm is possible with electric power. It's just not the best way to get an electric power system to yeild the same performance as the old 2-cycle .61. Spin a bigger prop a little slower and your prop will get better traction and you will get to enjoy longer flight times and quicker acceleration.... but do as you will. If you like spinning an 11x7 at 15K, whose to tell you your wrong? Certainly not me.