I'm interested in translating the Suikoden I & II PSP game so I found the thread below that talks about isolating gzip files from a large file and decompressing them. 
http://www.romhacking.net/forum/index.php/topic,10159.0.html

I was successful in creating a program that extracts each of the files and decompresses them, but before I start the translation process, I want to make a companion program that re-compresses the files and inserts the information back into the original file.  Unfortunately, the two ways of do this (manually with gzip or automatically with C# GZipStream) produces a file that is larger than the original compressed file.  Any ideas on why this would happen?

I am happy to provide any files or source code needed to solve this issue.