One thing that worked for me but I haven't seen mentioned in the
Firebreath community is UPX. It's a compressor for executable formats
like .dll files on windows and .so files on Linux.
http://upx.sourceforge.net/
It's completely self-contained meaning that after you compress the dll
or so file, it still works exactly the same. The final size of my
NPAPI plugin's binary file was around ~600k when I compiled it with
MinRelSize and then compressed it with UPX on Windows and Linux. I
couldn't get it to work for the OS X binaries.