Impressive project, and well underway!
I'm curious about the primary cell. What is the construction? The components appear to be carbon fiber over a core I can't identify.
Carbon Fiber over Nomax core which is used in plains and NASA, it is a fiber material that absorbs the epoxy and becomes very stiff but light and when combined with the top and bottom layer of carbon fiber it is hard to beat. I have added a better view of the layers and also added a better photo of my 8" secondary.
I'm not familiar with primary mirror cells made of this kind of material, I built a few from a combination of carbon steel, 6061 aluminum alloy and 316 stainless steel bolts and fasteners. Are you using carbon fiber composite to reduce the weight but maintain the stiffness, or are you using it to reduce thermal issues? It certainly won't have the coefficient of expansion that steel and aluminum do when made of carbon fiber composites.