One note on using RTV...
Let it set up for about 30 minutes BEFORE tighening down those screws. This lets the RTV form enough of a cured "skin" to make a true gasket. If you tighten down the screws all the way you are pushing out the sealant and allowing possible leaks. You WANT that RTV to be compressed like a gasket and not squished out like grease.
This technique has worked well for me in the past on automotive as well as water block construction.
On my current reservior, I have a gasket that was created simply by putting RTV in a home made injection mold (two pieces of acrylic with a milled relief and injection holes)... I let it cure 48 hours as it didn't have much area exposed to the air. After removing it I let it cure another 24 hours outside the mold. I now have a gasket that is about 1/16" thick and is compressable and reusable.
