Change the mercy hp to whatever you think, Ive tested 50-200, change the range if you want. It works don't to range 6 I think.
Then load the game non faf with your mod, enable cheats, give yourself a mercy and the enemy a t3 pgen, Omni and 1 flak. Have the mercy target the flak. Add more flak till your happy.
Lol once I gave the mercy like range 2 and it would fly over and not target then circle back to it and activate. At 200 hp 1 flak couldn't stop it even flying over twice