Thickness?

I just used regular clear house silicone. Worked fine for years. But liked said before its a pia to get all off after I cracked mine to replace. Next time I will not use as much silicone.

Where is a good place to buy mirrored tinted acrylic?

Theres a place in Cleveland on w.150th, forgot name. A little south of Lorain rd.

Or you could maybe try House of Plastics just east of downtown....

http://www.hpmanufacturing.com/

With the advances in vinyl wrap materials, why wouldn't you just get the chrome/mirrored vinyl and stick it on?

Or do they make a mirror finished Mylar with an adhesive backing?

I have installed large mirrors underneath an engine hatch with 4200. I never had an issue with cutting, drilling, or engine heat. They do sell a special drill bit which is evenly tapered to help prevent gouging, which leads to cracking. As previously mentioned......drill and/or cut very slow.

Thanks guys for the info. Im going to pick up glass this week. Ill keep you guys posted.

drilling it slow usually not the issue, but cracks coming from the holes after been on for a while is what I've seen...

There is a plastic shop next door to where my office is. If you have a problem you can pm me and I will get it for you and have it pre drilled. When we replaced mine there was .5 inch plywood that it was glued which was the same shape of the mirror. After it dried I then screwed it to the hatch. I have no problems at all