The default is 50MB, but most organizations (I have seen) are using
~100MB. Remember, the higher you make your unload size, the greater
chance the connection will timeout. You can modify the timeout settings
in IIS manager for the Web Service, but don't go crazy! If set too high,
I assume legitimate errors could take a long time to self-correct and
timeout.
Bottom line: The slower the WAN, the smaller the upload size. To
increase WAN upload size, increase timeout. Maybe one of the developers
can tell us what else breaks by raising the IIS timeout setting?