Geo, would it be possable to do a script that only included the combat log in the zip file if the combat log has changed since the prev turn? this may save a bit of upload bandwidth on your side, and some download bandwidth on ours.
if you did do this you might also want to give players the option to download the combat file seperatly incase they play on multiple PCs
if pbw was in python I'd try do a script myself,
infact I might just do that for the next version of PBFTP