Thanks for the info...
This tank will be next to another 55 (already in place)- and I'd like them to be at the same height. That was part of my motivation to find out what bottom support was necessary.
For tank leveling, I used to use a sheet of homasote(?) - greyish, a little spongy, maybe 1/2" thick, on top of plywood, on top of cinder blocks.
I like the weather stripping idea. The width is the same as the iron the tank sits on - what thickness do you suggest?
For anyone interested in details of tempered glass, I found this post:
http://www.thekrib.com/TankHardware/glass.html#7
Thanks.