I made a thread on build a Frame less thank not too long ago, can be found here,
http://reefcentral.com/forums/showthread.php?s=&threadid=1599948
lots of good tips and info, i am still in the process of getting the tools needed, bar clamps and corner clamps along with other miscellaneous.
As you can see in the Giga was using GE RTV100 Series silicon and it turned out good, which Chimpers also recommend.
I went to a Glass & Aluminum Manufacture for price quot and got these based on 42 x 42 x 18 tank.
Sides 18"x42 " 3/8 thickness:
3/8 Standard glass "tempered" "Polished" $50 each
3/8 Starphire 150 "tempered" "Polished" $120 each
Sides 18"x42 " 1/2 thickness:
1/2 Standard glass "tempered" "Polished" $82 each
1/2 Starphire 150 "tempered" "Polished" $150 each
Base 42"x42" 3/8 thickness:
Standard glass 42"x42" 3/8 "tempered" "Polished" $125 each
Starphire 42"x42" 3/8 "tempered" "Polished" $170
Base 42"x42" 1/2 thickness:
Standard glass 42"x42" 1/2 "tempered" "Polished" $270 each
Starphire 42"x42" 1/2 "tempered" "Polished" $350
I am planning on going starphire, there are a couple corners i could cut to save on over all cost, firstly use standard glass for the base, 3/8", with a tank at 18" tall based on the GARF's build your own custom tank tool:
http://garf.org/tank/buildtank.asp i could probably still use 1/4" glass thickness which would be alot cheaper, anything over 18" would have to be 3/8".
I am still doing a massive research on this, i am waiting for my new camera to arrive so i can start taking some pictures of other custom tank build by Elos at a local reef shop.