I tried to download your SSU (Space shuttle ultra) 4.2 from the /resoures section, but there is no download link. It says "We ran into some problems: The addon is private".
Is there a way to download SSU 4.2?
Well, I installed a new Version of Blender on Linux. But I can import add-ons for Blender in Linux too. And actually I can build my own nozzles. But yes, it would be nice to compare. And It would even more nice, if I could use parts. Like the RCS thrusters from the SM. My Addon will be on top of a S-IVB and under a SM inside a Skylab-Shroud. I could use these parts in Blender to figure out the measurements.