It has been answered already.
http://gbatemp.net/index.php?s=&showto...t&p=2359720
Check that post, the rest of the page and a page before and after for the discussion about that.
I'm not sure that addresses the same thing. Please excuse my ignorance as I don't know how it works under the hood, but I'm guessing that in order to pass the GAMEID to Disc_SetWBFS, you already have to strip out the .wbfs extension from the filename to get the GAMEID. I'm suggesting (actually, it was originally suggested by 0ld8oy) to strip out everything after the first 6 characters instead.
If it's not that simple, no big deal. The goals I had in mind were:
1) reduce the number of files in the wbfs directory
2) keep it easy to see at a glance the game that each file represents
3) maintain compatibility with the existing file structure
I guess I just have to copy my answer again:
QUOTE