I don't think you can do this. The SETI@home servers would need to be listening on whatever port you could change your client to. I'm not even sure what port SETI@home runs on.
I'd shoot an e-mail to their support and ask if there is a way. I think they have message boards too but last I looked they were all screwed up.
P.S. I see the Cult of Sager team page has not been updated since the 10th. Is that normal?