No. "Advanced" network configuration options such as manual IP addressing and manual port selection aren't available with the Slingbox 350 or 500. It's DHCP or nothing (although you can use a static DHCP reservation if that's an option). You also could use any of the Slingboxes other than the 350 or 500.
Along the same lines I can't get to my Slingbox 350 from work since I can't select a port I know is open on our firewall, so my seven-year-old Slingbox AV continues to have a useful feature my 350 does not.