Jumbo Frames and Xen don't mix well

It seems that while the pethN and ethN in a dom0 can be set to support jumbo frames the bridge that connects them cannot. Some symptoms are ssh works but scp does not, pings the size flag set to overflow the standard 1500 mtu fail, ifconfig xenbr0 mtu 9000 fails. This was tested with xen 3.1 and rhel5.