I too am lerning with an lt40 on grass and had grass mowing problems to begin with. I had an 11" prop which bogged badly on takeoff. I switched to a 10" which helped (but is not a recommended prop for my 46 LA). I've also taken the 2.75" wheel from the nose (along with another one I bought from the hobby shop) and moved those to the rear and took one of the 3" rear wheels and moved it to the front which gives it a more nose up attitude. I haven't flown it yet since this mod, but it is something you might consider. Whatever will reduce my need of 409 and paper towels to remove the green from the whole plane.

Wayne