Adding a 7.5 client to 6.5 master.

Hi all,

I have a situation where client is demanding me to add netbackup 7.5 client to a master server with netbackup 6.5 version. At first I denied him that we can not add higher version client to a lower master server. I asked him to downgrade the client version. But he is not ready to do it. Is there any alternate way to overcome this.