sophos v5 updating

[Mark Nienberg]

I'm installing a new MailScanner server from scratch, so I have the 
opportunity to use sophos 5 instead of sophos 4 if I want to. I've read 
the wiki and I have the latest MailScanner so I can use MailScanner's 
sophos installation script. On the Sophos download website I see that v5 
download file is 50Mb, while v4 is only 12Mb. I suppose that is because 
v5 has on-access scanning capability, that we will turn off anyway for 
use with MailScanner.

If I use v5 will I have to download a 50Mb engine update every month? 
Although I have sophos EM library running for my windows workstations, 
I'd prefer the mail server to update itself rather than relying on a 
windows machine.  What is everyone else doing?

Thanks,
Mark