MOJO,

correct, it was the poor man's fighter jet. but that does not mean it was limp. the US air force did used it in vietnam for evaluation purposes only.

the "F5" trainer that the US airforce you refer to is actually the T38 Talon, an F5 twin/look-alike and was actually the predecessor of the F5.

"F-5A Freedom Fighter

The F-5 is a supersonic fighter combining low cost, ease of maintenance, and great versatility. More than 2,000 F-5 aircraft have been procured by the USAF for use by allied nations. The F-5, which resembles the USAF Northrop T-38 trainer, is suitable for various types of ground-support and aerial intercept missions, including those which would have to be conducted from sod fields in combat areas.
The F-5 first flew on July 30, 1959 and deliveries to the Tactical Air Command for instructing foreign pilots began in April 1964. Pilots from Iran and South Korea were the first to be trained in the F-5, followed by pilots from Norway, Greece, Taiwan, Spain, and other Free World nations which have adopted the F-5. A two place combat trainer version, the F-5B, first flew in February 1964. In 1966-67, a USAF squadron of F-5s flew combat missions in Southeast Asia for operational evaluation purposes."