I won’t have time, since I’m not running Rhino on my current computer.
A while ago I posted an unfinished gh adding here.
It offers some components you might find useful:
It offers a working flange/draft component, you can crown and extrapolate surfaces with it. It may be helpful for you. Be aware, i never finished it, and some functionality is not working well. Also make sure to stay on non-rational Beziers.
Also have a look at the section I have posted in the other thread. that should be a guide line.