A .40 will pull it, a 46 would be a better choice. You'll have more power when you need it now and you'll have a bigger engine that you will want on your second (non-trainer) plane. It never hurts to have too much power as long as it doesn't add too much weight.
an evolution .46 would be agreat choice engine for ya. About the same price as the la .40 but tons more power. if you go to the swoomp vids from tulsa my extreme flight 540 in is powered by an evolution 46.