Would, instead of a CF plate, a scrap 5"ma pyrex elliptical blank be better as the surface to adhere with RTV the 6"ma pyrex mirror (using the same dot pattern, thickness, etc)?

The scrap would have at least 1/2" thickness to cement into the slip-fit 5"ID CF tube, and it would have the 1/2" aluminum push-pull alignment plate inserted into its other end.

Thoughts?

Steven