Just make the bottom piece a little longer than the standard slimline kit tube (about 5/16"). This leaves a little bit of the wood "unsupported" by brass. Not sure if that is good, probally not terrible, but not as good as using a longer tube to begin with. The nib end should be flush, the twist mechism goes into the "bare" wood end. The cap is standard tube size. by removing the centerband, you can make the middle piece any width you want. They just butt up against each other. As I said before, I got this off of a video, not my idea. I'm as creative as a rock. I can duplicate alot, but create little :lol:.
Be on the lookout, I am going to offer both my DVDs up for loan after the first of the year, first asker gets em first...