@rich o brien said:

But how does SU read UDIMs? Separate maps? I know I read about this before with some other model you did but can't remember the workflow.

I did a quick recap in the thread about the Ferrari F2004, which was actually a pretty complex model.
Here's an extended overview of the full process I use to prepare the model for the cuts, the packing of the tiles and the final reload (including some tricks for unfolding flat strip throwing in a bit of Thrupaint and also to create an ID map straight in Sketchup). I'not sure which is the worst, if my english or my michrophone, but I hope it's itellegible enough. 🤣