Check the priced difference between the 40 and 46 engines and then buy the 46!! I have seen some hobby sortes where the price is the same between the 2 engines. The extra oomph can be very handy on grass fields or when the wind whips up and you want more power to get back to the runway in 1 piece. A lot of trainers come with 10 oz. tanks which is all you need for a 46 engine. If you got to try the same plane with the 2 different engines, you would not want to go back to to 40 engine after you tried the 46!!!