nah there is no specific path for helicopters as u can deploy them at any side of the map and rally them unlike other air units, if u succeed in blocking helio attack that means the attacker is dumb not ur base design, however there is only one plan that may work which is putting many ambushes and traps inside a closed block around ur oil refinery so raiders are forced to attack the soldiers from ambush instead of refinery no idea if it's completely effective or not but a game breaker in all ways to render all ur ambushes useless for protection against helio attacks