Trying to Liberate All Outposts as Fast as Possible Without using Helicopters, Planes, Boats or the Wingsuit.

The most challenging Outposts in the game are definitely Seed Ranch and Whistling Beaver Brewery because they both have 3 alarms each that are spread across the whole Outpost, making it difficult to destroy them all before any cultist goes and sets them off. Sub 45 is most likely possible with a perfect and flawless run.