I wonder how much gain one would see from using pack200 over normal zip jar at these very small sizes?
IIRC from last year, probably at least 2k of uncompressed bytecode. As a rule of thumb, with all the tricks available you could get just under 8kb into 4kb (about 50% compression). I'd expect to get at least 10-11kb into 4kb using pack200, something like 37% compression. It's really quiet a difference (again, iirc).
In the end, it really doesn't matter. The 4k contest always comes down to gameplay, not technology. I'm just making the case it'd be nice to have the breathing room