Reducing File Size

[denbigh7]

I’m editing some belts in the bgETC Pac file. When I inject the new textures, they are identical in size and inject just fine. But after injecting the 0000 texture file into the belt file (in this case, 0043.pac), and then injecting 0043 back into the bgETC file, the final bgETC file is about 46.50mb as opposed to the original file which is 46.05mb. 
No matter what I do, I can’t get it working in the game. Any suggestions?

thanks!