nanotube necklace

Here's another in my series of explorations of nanotube forms. It's quite symmetrical, and I'm now working on one that's asymmetrical, but both are based on my attempts to make tubes that curve and get bigger and smaller to create a design. I just read Cindy Holsclaw's post on her beadorigami blog about chiral forms in DNA, so I'll mention a bit about that. The beaded molecules blog shows chiral and achiral forms for their torus structures. Generally the chiral forms seem to make the smoothest curves, which I like the look of. However, unless I make a necklace long enough to fit over a person's head (which I'd like to do, but haven't) I need to be able to endcap the tube, or at least to have it end smoothly so that I can put in a clasp. That seems to require an achiral tube. I've also found that I can change the diameter of the tube as I go around a curve, for example I can go from a 6-hexagon circumference to a 5-hexagon one. If I try to do it on a straight section it sort of bumps in on one side, and doesn't look good.