My concern is why you can't just do the auto or manual update for the VPS signatures as they shouldn't take minutes, even on dial-up, but seconds to update. You didn't answer what connection method you have.
Once you have the complete VPS file, installed then any future updates should be incremental only downloading the latest signatures that have been added. Typically this is a download of around 25-50KB often less today's update was I think 15KB.