I had one of those. Certainly, it is not overwhelmed by power with the 40LA.... but if it is boring with 40 I don't think it will become much more exciting with a larger engine.

Before a new engine, you might want to try pulling the exhaust baffle and running 15% fuel. You may gain another 10-20% power. Certainly, the fx engines gain with improved exhaust. The la's should gain a bit as well... perhaps not as much, but some.

The 40la has just enough ooommph to pull through a small loops, stall turns, rolls, immelmans, split-s's, etc. As I recall.. the stall turns where quite nice.

For more fun, excitement, and challenge why not try something like running through the sportsman aerobatic pattern sequence. The plane should be able to get through it. It takes some practice to do smoothly and will force you improve your skills.... no cash outlay!

Are you running an 10x6? You'll get more low speed thrust from an 11x4. I'd give it a try for kicks. I find lots of thrust for good vertical lines is more fun than raw speed... that's me.

I'd also suggest a 46fx if you do upgrade.