F20/40size
All I can say is it is a great sports model with good jet like flying capabilities. It probably is going to be a bit quicker than the 60 size version IMHO, especially if you shoe horned a 60 size donk in up front. Mine is 4 Y.O. and still going strong ....I installed a O.S. 61 in mine. Makes a great D/F or turbine practice model.