[morzh]

PuhPow

You are probably right.

I am not sure about the big ones - the holes seem to be a bit larger than those posts but could be still.

Both smaller and larger flatter ones fit in those mill-outs under the chassis, in the board, so they are probably to cushion the chassis. Why they need the holes...not sure, there are no through screws that go there as there are no through holes drilled, so it is just padding then and the screws go separately in some other place. I guess they did cushion the heck out of that chassis.....it's a heavy one.