Chuck, I used silicon adhesive to hold my 16" mirror in the cell. Since it is a thin mirror 7/8" plate glass, I used a regular 18 point support for the back of the mirror. I used stick-on felt pads for points. On the sides I have steel brackets that stick up with about a 1/2" gap around the mirror. They have a hole drilled in them. After I placed the mirror in the mount and centered it properly, I put silicon through the holes until it was just touching the side of the mirror, maybe 1/4" touching the mirror. This appears to hold the mirror properly without pinching or uneven pressure. It also keeps the mirror from falling out when pointed down or being bounced across the meadow at Monte Cristo. My mirror is barely f/5. I will never make a short mirror again. It has to be too precise and the collimation has to be too accurate. I use a laser and a Cheshire to collimate when I want to view all night. The laser is good enough for most of the public events. I think my next mirror will be a 20" f/10 or so, Yolo. This will give me the advantage of no ladder while still giving me a long F.L.. Dave