i have had a 180gal rimless (4'x3', 24" high) from glasscagescom for about 6 months now. the silicon is very neat, extra bracing on the bottom, with custom overflow, and in perfect condition. and that this size tank was made from 3/4" plate glass, it is truly built like a tank, and quite heavy. i paid a little extra to have it delivered to my job, so that i had access to a fork truck to unload it (considering that the tank weighed about 420 pounds or so).
when the wife allows, i will be getting another large tank from them.