For all you tank building engineering types....

[jostafew]

According to this calculator you have a safety factor of around 5
http://www.theaquatools.com/building-your-aquarium

For comparison my professionally built custom rimless is 30x24x24 and has 1/2" glass (12mm) which comes in at a safety factor of 5-6. I think you're fine at that thickness.

[sphelps]

Sounds fine to me but I would assume the glass is 10mm and not 9. A good test would be to measure the max deflection of the glass when the tank is full (how much the tank bows) as that's the major design criteria for rimless tanks.

For reference my tank is 54" long and 20" tall and uses 12mm straphire.

[ScubaSteve]

The aquatools calculator assumes rimless though they don't state it, so a safety factor of 5 should be fine. 7 to 9 is overkill. I use 10 mm glass on my rimless 24x24x20 tank. My friend has a rimless that is about 31.5x14x18 and it uses 6 mm glass (though I could not say whether it is tempered or not.

[rstar]

Thanks for the advice guys, I feel much better about it now, and it is 10mm glass, I measured from the sanded edge and it doesnt account for the slight bevel too the glass.