I was merely thinking in terms of increasing the overall mass of the Flying Castle to bump up our kinetic energy level enough to help fling us out beyond the Solar System.
Besides, we will need some company traveling through interstellar space--It's a long way to the closest star.
"... we will need some company traveling through interstellar space--It's a long way to the closest star."
The easiest way to get them is the old-fashioned way. Any trip to the stars with our current technology would take generations.
We have to be careful about adding mass. We will have to accelerate it, and then decelerate at the end. We want to be "lean and mean." Well, maybe not mean, just prepared.
We will need "defenses"; against space debris if nothing else. We also need to accelerate our reaction gases to the highest rate possible. I'll take care of that, but we don't want unnecessary mass.
Possibly, we'll use light sails at our destination like a parachute. Or maybe we'll drop small colonies en route like Johnny Peopleseed.