I found that Mechjeb got it into orbit, but with some difficulty- I tried to get to an 80km orbit, and it was doing fine in the gravity turn until about 74 when the angle got wonky. It managed to make up for the shortfall in the Apoapsis by burning afterwards and got to an 80km orbit anyway, but it was a near miss. And yes, it does want to tip over. I found this a problem, I think you\'re right about the side engines but maybe some wings/fins would help too.