It is not tempered... the bottom pane of glass is, because it is maybe only 1/4 inch. I think I may just mimic the glass on my 155g and do 48"x 30"x 1/2" thickThe glass on the tank you measured is probably Tempered. I have a tank with those exact measurements.
Are you getting tempered glass?
If not, It may be ok with the frame but with this kind of thing I always try to be extra cautious.