Yeah id somehow go with 2-3 pieces of glass for the front with supports between each piece and along the top.
If you can buy a 5ft tank relatively cheaply then you could do it I guess, the height is a problem though, just for comparasion I have a 4ft tank thats 900high and its made from 15mm glass I guess you would need somewhere around that for your tank, how did your dad go about getting his glass and what thickness did he use?