Precomputed visibility + instanced static meshes

Hi,
In order to minimize draw calls on a GearVR game, I try to use both precomputed visibility and instanced static meshes but it doesn’t seem to work very well. It looks like all instances of an instanced static mesh are considered as one big mesh when precomputed visibility chose to occlude it or not.

Let say I have some boxes, all those boxes are instances of the same instanced static mesh. One of those boxes is in front of the character with a wall behind this box and all of the others boxes behind this wall, then, because the character see one of the box, the boxes behind the wall will be rendered and never occluded.

Is it supposed to work like this or am I missing something? Does the precomputed visibility occlude every instance even when some of them are not visible? Is it possible to use both or do I have to chose only one of them?

Well it’s even worse that what I tought, if the player look at one instance of the mesh, all other instance are rendered even if they are offscreen (like in the back of the player). At least this what I understand when using the “FreezeRendering” command