The iClooly is the pen I've been using most for quick sketches on the iPad, but for longer sketches and for drawing the handwritten font I'm making in iFontMaker, the short stick kind of sucks.
Extending the iClooly stick is an easy hack that almost doesn't merit a post: rip off the back, take apart a mechanical pencil, and mash the two together.
Verbose version: Remove the clicky end and the spring inside, making sure the brush is pressed down and the bristles exposed. Find a cyclinder that the iClooly will slide into--I'm using the plastic housing of a Sanford mechanical pencil--and push the iClooly into the cylinder.