I spent the days before Christmas working on a 3" version of my Tank. I machined two spherical end caps and they looked good up to the point I CNCed the lacing posts . I ruined one of the caps and need to make another.
I did to some ln2 tests with the end cap. With the PET tube filled with Ln2 it does not leak or break, and the PETG still seems flexible.
You won't here from me much for the rest of the week as this is my 20th wedding anniversary and we are going away for a few days.