You sure did, any weight in the data.ini is in kg.
But: int. fuel F-5E/F = 677 USgall. =2559 liter= 2073 kg
int.fuel (N)F-5A/B/CF-116 = 583 USgall. =2203 liter= 1786 kg
Tiptanks = 2 x 50 USgall. = 2 x 189 liter = 2 x 153 kg.
This makes a total of 2093 kg for the (N)F-5A/B with tiptanks and it depends how you fly it.
The tip tanks cannot be jettisoned as the (N)F-5A/B needs either the tank or the missile launcher on the wingtip against flutter. In the SF2 CF-116 the tiptank seems to be an integral part so probably the 2093 kg is ok.
In the NF-5A the tank is optional, so I think 1786 kg is correct. Fuel is JP8.
According to Canadian Profile Canadair CF-5 by Bob McIntyre, the tip tanks give taxi and take off + 2 to 3 minutes flight.
Apart from that they have an aerodynamic effect (less drag, no wingtip vortices) and - like in the F104 they act as endplates on the wing giving a marginally better turning performance. The NF-5B never had wingtip missiles as it was never used - like the NF-5A - as an interim fighter on QRA duty during the transition from the F-104G tot the F-16A of the first two KLu interceptor squadrons at Leeuwarden airbase.
Other info is from Joe Baughers website and from a Dutch book on the NF-5 by C.J. van Gent.
This whole thing is explicitely NOT meant as whining or rivet counting, but please, please, please consider it as an attempt to contribute to an even better airplane.
Hou doe,
Derk