Convertible Pencil Rocket (Parametric)

Update 12/1 - v1.1 See below!

When I was a kid and bored in class, I used to pretend my pencil was a rocket launching from my desk. Now, don't get me wrong here -- I'm not trying to squelch the imagination of any little kids who dream of being astronauts some day; I'm just trying to help those pencils fly a little straighter so they actually stick into the ceiling like they're supposed to.

So what's this "convertible" business all about, you say? Well, that's the real beauty of this desig