One of the downsides of Strawberry Perl's move from the InnoSetup
Our headline installer went from 17meg to 32meg overnight.
If you were paying (stupidly) close attention to the latest release, you might have noticed that Curtis managed to drop the installer by 3meg, without changing (at all) the compression mechanism and while adding slightly more content to the package.
Via the curious method of just changing the order in which he added the files to the archive, sorting by file extension instead of sorting by file name.
The grouping (even at a naive level) of similar types of content into the same area of the resulting file provided such a good improvement to dictionary efficiency, that it resulting in nearly a 10% improvement over plain deflate (which is almost as good as switching to bz2).
What would be even more awesome would be combining this change with LZMA as well (which builds dictionaries across much bigger areas of the file).
And if you could do it in something less than O(n^2) time, it might also be interesting to test pairs of files directly, to brute-force discover which file order was most efficient for feeding into the compression routine.