This is a beautiful mod and I can tell a lot of effort went into it. It is very fun to fly and I love the fact that you can detach the two stages. I do hope more will be done to improve it in the future, such as a cockpit view and sound. Perhaps there is a way to fix how the camera view freaks out when it's flying vertically?
I've been wondering how well the engine would do with space stuff.. That's a fun step in that direction. Great work :) Next up, to scale? :P (I realize the engine would probably go crazy first with the numerical-precision-related shaking at larger scales)