Completed test of new test version, settings (ugrids 5) and highly modded game
ExpandSystemMemoryX64=true
ReduceSystemMemoryUsage=true
DisableDriverMemoryManager=false (doesn't seem have much impact either setting)
ReservedMemorySizeMb=1024
EnableUnsafeMemoryHacks=false
Exterior worldspace very smooth and stable - very little stutter on loading cells
Still having some issues with infinite load screens though, sometimes when fast traveling to Solitude, or when in Solitude and I try to enter The Blue Palace. This happened on my last test, at the time VRAM was 934mb RAM was 1035mb. I have Vsync enabled along with FPS limiter set and physics fix enabled so not sure what causing this.
EDIT: new test (updated SPM) infinite load screen fast traveling from Markarth to Solitude:
i7 3770k @4.1hz, 8gb Corsair RAM, 3GB EVGA GTX 780 SC+ACX Cooler, OCZ Agility 240gb SSD, Windows 7 64-bit