Kdat permissions

Can someone piont me in the right direction to set the permissions for kdat to work for a normal user ? I have created a group "backup" and added myself to it and set the kdat executable to user = root group = backup but it wont find a tape in the drive or even the drive /dev/st0 everything works ok if I login as root. So I must be missing something. ps Anybody want some DDS2 tapes or 1xDDS3 my drive is DDS1 pps I will be at the meet Thursday giving away an Amiga 4000/030 if the wife lets me have the car