> Maybe I'm asking something easier.  I can't figure out how to set up 
> a BalloonCanvas and draw a Balloon bezier curse on that canvas.

Try this:

(Display getCanvas asBalloonCanvas)
	aaLevel: 4;
	drawBezierShape: {
		0 at 0. 		100 at 200. 	200 at 0. 
		200 at 0. 	100 at 50. 	0 at 0.
	}
	color: Color white
	borderWidth: 1
	borderColor: Color black.

Note that the points spezify quadratic bezier segments, e.g., the first
three points define the first segment, the next three the second segment and
so on. To insert a straight patch make the intermediate (off-curve) control
point the same as either start or end, e.g.,

(Display getCanvas asBalloonCanvas)
	aaLevel: 4;
	drawBezierShape: {
		0 at 0. 		100 at 200. 	200 at 0. 
		200 at 0. 	100 at 50. 	100 at 50.
		100 at 50. 	0 at 0. 		0 at 0.
	}
	color: Color white
	borderWidth: 1
	borderColor: Color black.

Hope this helps,
  - Andreas