John says "good grief" start with big wheels and a 11x4 prop and from a cost standpoint he is right. However, as I pointed out the landing gear is short on a Superstar 40 and the 11' prop puts you deeper into the grass cutting business but go ahead and try it, not much money involved in a prop and tires. Save the engine upgrade for step #2. I'll bet you still need the enging upgrade, but of course I'am not always right! I know from having flown this combo that once in the air the .40LA will fly the airplane just fine, it's just a problum getting airborn with tall grass. Give us some feedback after swaping tires and prop.