I used my ShapeJS.com pentube generator to create these red SF tubes for the Panache pen. This two-tube screw-together pen can stand vertically on its wider end. https://www.woodturnerscatalog.com/p/2/2750/Artisan-Panache-Pen-Kit The smaller tube used for the cap came out a bit warped at the thinner end. This required some careful gluing and trimming of the ends (including the brass tube). My guess is this happened because the material isn't of constant thickness around the tube. The issue was likely exacerbated by needing to go to the minimum wall thickness of 0.7mm at that end of the tube so the decorative pattern would be revealed. It might be less of a problem using frosted detail or HP plastic for this particular design. If you look at the narrow end of the smaller tube you can see a small mismatch between the black band and the end of the printed tube. It's not terrible but it's also not desireable. Here's a screen grab of the parameters used for these pen tubes.