What is the difference in the power of an OS .25FP and an FX? is it relevant? I bought an engine on RCU classified and it showed a "stock "photo" of an FX but in the description the guy stated it was an FP..it was $35 so I'm guessing it will turn out to be the older FP...btw a .25 is BIG for me as I fly mostly 1/2-1A .049-.074....Rog