The FighterResource2 takes the file size of the FitChar.pac, FitCharMotionEtc.pac, and FitChar0X.pac and totals them up.
If it's above a certain limit it'll crash.
There's a code that Brawl Minus and Project M both use to increase the limit a little though.
Memory Extention for FighterXResource2 [Dantarion]
* 04421B54 00096600
* 04421B74 00096600
* 04421B94 00096600
* 04421BB4 00096600
* 04421E1C 00096600
* 04421E3C 00096600
* 04421EBC 00096600
* 04421EDC 00096600