> What pipe sizes are you using?

512 Kbit/s for the upload pipe
5696 Kbit/s for the download pipe

> I assume you've measured them using a
> real-world throughput test rather than relying on the speeds your ISP has
> quoted?

Sure I've tested the down- and upload speed before. I've reached ~ 
712KByte (5696 KBit) down
and ~ 64 KByte (512 KBit) up.