That's a great thread, Steven.
Here is another thought, but it gets complex. However, you can play with the K-factor or Y-factor to make up for the distortion through the bends.
I followed the tube with 60.3mm thick sheetmetal. The twist causes a problem in that it untwists in making the end cut. This has to be added -correctly- in a subsequent feature instead. However, you can take data from the master to achieve this.
