Question SIze of mesh reference in memory

HI,

I am having some seroius memory problems with some meshes; one mesh is taking up to 3GB in memory. The particular (skinned) mesh has 70K vertices in 6 submeshes, and around 500 blend shapes.
If I switch normals to be calculated, the memory usage drops to around 1GB, which I think is still way to high. So questions:
1) What is causing the excessive memory usage? And why does it change if I switch to calculate normals?
2) How can I reduce it?
3) What is best practice do load / unload lots of bigger meshes during runtime? If I have them as inactive GOs, they are still occupying memory.


Thanks!

 

Update: the Memory consumption comes mostly from blend shapes. Which leads to the question: is there any way to reduce the in-memory size of blendshapes? Why does it change drastically if I change to calculate normals? How can I reduce it further?