I'm going to rebuild my 12 " cell soon (pictured ) and have been reading a little on them lately being used by atm ers.
My current cell supports a ring of velcro around the 60% zone two edge supports which the mirror just rests on , in a pull only adjustment.
I don't have any problem with the velcro it holds the mirror well
I have allways noticed a tiny bit of deflection in collimation through alt motion, which sits with the 5 + kg weight of the glass distorting the springs a bit , I should of used a push pull design when I made it , but if these disc springs minimize distortion and don't put any differant loadings on things it might be an easier fix.
