I started flying my LT40 with a 46LA. I fly from a relatively short field surrounded by trees(or perhaps more correctly TREEEEEES!). Immediately after take off you have to start a climbing turn and continue the turn to be above the trees on the downwind leg... including a 100ft cottonwood which has grabbed a number of planes. The 46LA/LT40 combination made the take offs a little more "interesting" than I was comfortable with. I then put a 46FX on it and it was a vast improvement on the LT40. The instructors were no longer shaking uncontrollably after take off. You could probably go to a 50 or a 61 size engine, but any more than that is just overkill. Personally I say hang a good BB 46 on it and you'll have a nice flyer with enough wheaties to get you out of a tight spot