Hi i wud have commented better if u have posted ur x-ray.. anyways regarding safety its definately safe and u can go ahead but concerned with the success of the procedure..look if there is horizontal bone loss then its very difficult that graft stays for long after surgery..these kind of surgeries are more useful and successful for vertical or angular defects..if its 60%loss then its difficult that ur gaps get closed with this surgery...i suggest u must have a second opinion with a periodontist.best of luck take care feel free to ask ne further queries