There's 2 ways of doing it. One is editing the fleet multiplier for the small/normal/large fleet settings when you start a game, that's in gameplay.constants.
The other way that gives you more control is to edit the FP research line. Each race has their own, like RESEARCHSUBJECT_MAXSHIPSLOTSTECH0 through 7 (8 ranks of research).
Each research subject adds fleet points to the previous. If you open 0, you'll see the base is set to 100 and it adds 150. 1 adds another 150 I think, and so on until it all adds up to 2000. So you can just change how the fleet points are added to get you to whatever you need.
It's the same with capital ship crews.