Glass and Mirrors - Installing mirror without mastic

I need to install a mirror 4' wide by 5' tall as the back of a display in an alcove. I've Googled mirror installation and read through this forum and most mention using mastic. I'd really like to be able to take the mirror down for painting, etc. As long as I make sure I hit studs, can I just install the mirror with a J channel at the top and bottom? The mirror in my Master Bath is 7' wide and 42" tall and it's held up by 4 metal clips (2 top and bottom) and no mastic (we've taken it down) for 17 years with no problems.

Also, what thickness would you recommend for a 4'x5' mirror?

Thanks.

Not an expert on mirrors, but they can be installed as you said with a chanel at the top and bottom. They can, if it looks suitable, be attached with mirror washers of different designs and materials if a hole is drilled in the desired location(top, bottom, corners,???). I don't think I would go smaller than 1/4 inch in thickness. Hope this helps.

The mirror should be 1/4". Install it exactly how you bathroom mirror is installed. When you purchase the mirror they should be able to supply you with the necessary hardware.

Thanks for the replies. Johnam, you would just use the 1" wide metal clips top and bottom instead of J channel all the way across?

I like the clean look of the J channel. We would use a 3/4" J at the top and a 3/8" J at the bottom, lift the mirror into the top J and set it into the bottom J. As you can imagine, the the measurement of the height of the mirror is very critical and you would need suction cups to lift the mirror since it's in an alcove. It would be easier for you to use a J at the bottom and clips at the top.

Great. Thanks for the help!