a 40 might be underpowered. I would recommend a 46 for the lt-40.

The lt-40 can do some basic aerobatics, but it is designed to be stable, not aerobatic. If you build it without any dihedral, you may get a little more aerobatic ability, but at the cost of stability. Another option is to build the wing with less span by removing 1 wing bay from each side. I have seen both these mods done on an lt-40 and it still flew well. However, if you have not flown before, then I would just build it stock. That way you will have an easier plane to fly.