Hitman 2 Silent Assassin [SA Rank] Tunnel Rat

I hate this mission. It's the epitome of random. The formations of the sentries are random, their activity is random, where they are at is random, your route is random and not assured, the requirement to secure the helipad hinges on the formation of the beginning and who is posted by the door of the target (since they can move to and not away), and ultimate no skill involved other than enemy placements. I tried killing both guards outside and still no SA. This is the only secure method. Shit sucks.