After some futher analysis I found that perl6.pbc and the perl6 binary both are about 11MB in size - and 1.3MB when compressed with gzip.
So if anybody actually wants to do something about the size, teach parrot's pbc_to_exe compress the pbc, and uncompress into memory upon loading. In the long run it might also be possible to come up with a more compact PBC format, but I guess that's much more work than compressing and decompressing. Cheers, Moritz