Right, I have just done the same with the F3, so if you do the following it should work:
go to the F3.HDV file, and add the following lines immediately after RearTireCompoundSetting=0
FuelRange=( 1 , 1 , 71 ) // the third figure is max amount of fuel, i.e. full tank
FuelSetting=19 // initial fuel quantity
NumPitstopsRange=(0,1,4) // the third digit the number of stops available to choose i.e. 0,1,2, or 3 so choosing 4=3 stops
NumPitstopsSetting=2 // how many pitstops shown initially
Pitstop1Range=(0,1,71)
Pitstop1Setting=19 // pitstop 1 initial fuel setting
Pitstop2Range=(0,1,71)
Pitstop2Setting=19
Pitstop3Range=(0,1,71)
Pitstop3Setting=19
IMPORTANT it does not seem to work if you leave any empty lines, so these lines should go immediately below the reartirecompoundsetting line and immediately above the AISlipReaction line.
If you try it please let me know if it works ok for you, back your file up first!. The individual figures can be edited to suit