So I played for quite a while on ugridstoload=17. Not a single crash.

There is one issue: people spawn at elevation. Then they walk. And they fall and die. So one can't just go through the game without killing about one person every time you reload an area. Not so good. BUT, the point, the 64 bit engine handles the memory load well. It looks amazing with open cities to look at the waterfalls from Dragonsreach's porch. The ones that come down from Riverwood.

I have no idea how to fix the script that spawns NPCs (and rabbits and such). But it's the only problem I've seen.

Can't revert back to 5 in a regular way. I can't remember if this is an old issue. Choose your ugrids and stick with it!

I suggest to keep it at default, especially now since quite a few people are having issues with NPC being at incorrect locations.