Use UMDGen to patch the files, then save as a (Compressed ISO). A CSO scrubs dummy data, making the game smaller (under 300MB) without affecting performance. This is better than a raw ISO because it saves memory stick space.
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We must be objective. The mod is not perfect. Enemy AI is dumber, some voice lines are missing, and the final helicopter mission glitches frequently. Also, there is no online multiplayer. You are here for the campaign and ad-hoc splitscreen only. Use UMDGen to patch the files, then save