I would actually make one bigger then that. A home made one that is HUGE and more tall then long like most aquariums would be better to house your frill.
Just my opinion,
:Hey I just saw that Crocodile Hunter special on lizards in Australia and got a good look at how big these frillies get. Now, the experts say that you need a 55 gallon aquarium but yikes, this is a big lizard. I'm thinking more along the lines of 70 to 90 gallons. What do you all think of the curved front tanks at oceanicsystems.com? My dragon is just about ready to graduate to his big tank and that's what I'm looking at.