Fitting the primary mirror into the cell?

[turboscrew]

I got my scope (300 mm / 1200 mm F/4) last June, and everything looked good, but a couple of days ago I noticed that the mirror had started "pinching".

I took the mirror off from the cell. I thought there might have been too much silicon between the support pads and the mirror. I carefully took off all silicon from the supports and the mirror, but I'm still not convinced that it wouldn't pinch if I put it back.

 

Does anyone have advice or pointers about how to mount a mirror into the mirror cell and how to do the adjustments?

 

Originally the floating supports (the two outer pads in each triangle) were glued (or siliconed) to the back of the mirror and even the holders were glued to the side of the mirror, 

My mirror cell looks like this (IMG_0637.JPG).

The holder bolts are slightly conical and so is the hole in the holder (doesn't show that well in the picture IMG_0642.JPG).

The hights of the holders are not adjustable, so the the mirror height needs to be adjusted instead (IMG_0640.JPG).

The middle bolt under the support triangles adjust the height of the triangles, and the white plastic pads can be adjusted as well.
The other two bolts under the triangles just limit the triangles' lateral movement.