that's right,that 4 or 5 mph that you will lose,using a 4-blade over a 2-blade is sure gonna hurt you! i hear this argument all the time. give me a break! if i start listening to all the crap about efficency,or lack there of in multi-blade props,i might have to go home and pull the 4-blade off my .o.s. .46 powered GP spitfire.lordy,the thing only flies at 100+now,that extra 4-5 mph sure would come in handy! just my 2 cents.