Jim,
I've built several refugiums, sumps, overflow boxes, etc. all from glass that I cut myself.
On my two tanks right now I'm using refugiums/sumps that I built myself with overflow boxes and such. I love to cut glass and build stuff!
With that, I want to warn you that if you aren't really used to it, and even if you are, you can make mistakes. Mistakes can ruin a whole sheet of glass sometimes.
I found my drimmel tool works very well to smoth the edges. Otherwise you will always be cutting yourself. Skin get more tender in the salt water.
I was all jazzed to build a tank too, BUT I found I couldn't buy the glass to make a 15 gallon for less that the cost of a pre-made 30 gallon! So I build my parts and customize, but leave the actual tank to the pros.
So, for what ever you end up doing. Measure twice, cut once, and use duct tape to hold the walls to gether while the glue is drying. I love this tip from LeeRoy at
www.garf.org.
Anyway, let me know if I can help further. I'm wanting to do a 'glass cutting workshop' with my club.
HIH