I updated without uninstall and none of my custom runtimes were touched. Additionally the stuff I added to the Poser 11 Content Runtime remained untouched. Also the python scripts I added to the main program files runtime remained after updating.

*edit; and I use 'external binary morph targets' without incident ;)

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W10 Pro, HP Envy X360 Laptop, Intel Core i7-10510U, NVIDIA GeForce MX250, Intel UHD, 16 GB DDR4-2400 SDRAM, 1 TB PCIe NVMe M.2 SSD

Mudbox 2022, Adobe PS CC, Poser Pro 11.3, Blender 2.9, Wings3D 2.2.5

My Freestuff and Gallery at ShareCG