I understand, but I look at as, structural integrity of the mirror. At 10" for it's weight I is very strong but over 18" they become heavy and less structurally stable. As a fitter and turner we had a piece of round bar 260mm Dia and 2m long(solid, good quality), the amount of flex in it was amazing, it was visually the best example of mass verses dimension I have ever seen. Gravity wins.
In the cell requirements, some of the very common EQ Newt's work great with only double sided tape straight to the primary holder, at least it won't shift when rotated in EQ fashion.
I went 15 instead of 9 to divide the the mass dependence of each point evenly. After guessing I sincerely recommend using a divider and stepping out your PCD, check twice cut once(or is that the other way?).
I hope I haven't stolen your post molland67, have we been of any help to you? At what stage are you in construction? Cheers
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