A bigger question on the role of adversaries, and something of (another) threadjack--why the F-5? As I understand it, the F-5 was originally used as an adversary because its characteristics are reminiscent of MiG-21s and below. At least to my semi-trained way of thinking, it's not really duplicating the performance of the higher-end potential adversary aircraft today. With as many FSU aircraft as are available on the official and unofficial markets today, why use a stand-in? Money?
For that matter, can't a newer, higher-performance aircraft duplicate many of the characteristics of an older one merely by restricting the performance, i.e. holding back from its limits? Why use an older aircraft like the F-5?
That may sound like a retarded newbie-type question, but I really am interested.