What we have is a metal 18" satellite dish mounted on a chimney. Chimney is located in center of home, 15ft away on all sides from any edge, to then drop down side of home. Would prefer NOT to run a ground along top pf roof for 15 ft. Can i fish ground threw hole of existing rg-6 wires, and continue to fish it down to cellar?? Is this within code, and safe for lighning strike??? Also what size wire.