Currently 72 seats in the Australian senate. Constitution says no less than 6 seats per Original State, also that each original state must have the same number of seats, nor can election method discriminate between states.
Let's pretend that the politics of changing this part of the Constitution is not a problem -- what would be a preferable alternative?
It's vital IMHO to retain proportional representation and split terms so a (relatively) large, even number of seats per state is necessary.
The issue of over-representation of Tasmania is an interesting one. On the one hand it's important not to silence entirely the voice of the little state to the south, but at the same time the question of fairness is important.