Leave thing alone with the .40, you will not gain appreciable power and run the chance of making problems for yourself by drilling and modifying things. The engine is very reliable, and not very powerfull compared to others but it does a great job of flying that plane and making it easy for you to learn. Make sure you have the best prop for the engine, probably a 10x5 or so and go enjoy the learning process. Next plane, when you are a competent flier, go for the bigger engine. Don't dink with something playing master machinist to gain 100 rpms and shoot yourself in the foot with reliablity issues. It ain't worth it.