Yeah I think that should be a good guideline. The exact layout of the UDIMs shouldn’t matter. The system is at least smart enough to avoid allocating a linear chunk of memory for the entire UDIM space. So you should be able to fit 16 4k UDIM sheets in whatever configuration you like, even if it’s sparse. UDIM support should also efficiently handle UDIM sheets of different sizes, so you can have some 4k sheets mixed with sheets of other sizes without wasting memory.