Mr. DJ,

If you look at the build manual pictures on Fly Eagle's website you can get an idea of how much room there is. It appears that there is room for a larger engine. However, it's not a very big airplane and I would caution you about letting it get much heavier.

From the flight videos it seems pretty fast with a P-60 and Super Bee. If you really feel you need extra power a Wren Super Sport would be your best bet (same size and weight as a 54 with 18+ lbs. thrust). They're great engines. I just took delivery of my second one, which is going in my F-16.

Joe