I was working on with with a old iMac case but never finished it.

I have found instead of using ATV sealant or even silicon that Double/Bubble Epoxy works great for sealing and bonding. It's water tight and water proof. I use the red packet stuff.

http://www.vobaker.com/adhesive/double.htm

Sadly you just can't buy a few packets, they only sale half cartons or cases. A half carton runs for 50 to 60 bucks.
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