The G38 looked lost on the nose before the cowling was installed, so a bigger motor will fit. The G38 provides plenty of power. CG might be an issue. I have BIG servos in the tail with all the other radio gear pretty far back in the cockpit area. I think you will end up needing to either locate your batteries in the tail or add weight to the tail to balance.

Here are a few pictures that were taken at our field (Jedburg Flyers http://www.jedburgflyersrc.com/ ).