I GOT IT WORKING!!!!
*Ahem*
All you need to do is this. First, create a championship and go to the page where it shows you the drivers championship results. Then back out of it and quit the game. At this point, you need to set all of the opponent values to 27. Then, you need to open the F1_1994.bch file (in the same folder). Find the GAMEOPT_opponents line, and change to 27.
Now comes the long-winded bit. Go down to your player line, it will look like this:
Name="Gary Kemp"
VehFile="SEASONDATA\VEHICLES\SIMTEK\1994_S941\1994_SIMTEK32.VEH"
RCDFile=""
FinishPosition00=14
FinishPoints00=0
FinishPosition01=25
FinishPoints01=0
FinishPosition02=19
FinishPoints02=0
FinishPosition03=27
FinishPoints03=0
FinishPosition04=10
FinishPoints04=0
SeasonPoints=0
PointsPosition=11
PolesTaken=0
OriginalGridPosition=21
CurrentGridPosition=21
ControlType=0
Active=1
Change OriginalGridPosition and CurrentGridPosition to 27. Then scroll down the list of opponents, and make a list of them. From this list of 21, it should be easy to work out the missing 6. Then scroll down to the very last one, which will be this one probably:
[OPPONENT20]
Name="Eric Comas"
VehFile="SEASONDATA\VEHICLES\LARROUSSE\1994_ LH94\1994_LARROUSSE20.VEH"
RCDFile=""
FinishPosition00=27
FinishPoints00=0
FinishPosition01=12
FinishPoints01=0
FinishPosition02=28
FinishPoints02=0
FinishPosition03=28
FinishPoints03=0
FinishPosition04=9
FinishPoints04=0
SeasonPoints=0
PointsPosition=11
PolesTaken=0
OriginalGridPosition=20
CurrentGridPosition=20
ControlType=1
Active=1
Or someone else, but it will be 20. Copy and paste this, then change the name, repoint the veh file and increase the grid position lines by one. I added Michael Schumacher and it came out like this, with changes emboldened:
[OPPONENT21]
Name="
Michael Schumacher"
VehFile="
SEASONDATA\VEHICLES\Benetton\1994_B194\1994_BENETTON05.VEH"
RCDFile=""
FinishPosition00=7
FinishPoints00=0
FinishPosition01=2
FinishPoints01=6
FinishPosition02=2
FinishPoints02=6
FinishPosition03=1
FinishPoints03=10
FinishPosition04=1
FinishPoints04=10
SeasonPoints=32
PointsPosition=0
PolesTaken=4
OriginalGridPosition=
21CurrentGridPosition=
21ControlType=1
Active=1
Repeat this until you have added all drivers, which should take you up to grid position 26. Save and close.
Finally, back into the main F1C folder. Open up your F1C Config file and change GRIDSIZE to 28. Save and close, and when you re-load the championship it should have 28 drivers! :D