1: To prevent the heli from despawning at the marker, you have to find a way to still have Phil interacting with the heli when you trigger the marker. An easy way to do this is to block his door with the fence. This isn't all you need to do though. When you get out of the heli (press F once), you need to immediately press and hold F again, even before the marker triggers (basically a double tap of F and hold).
2: Land the heli as close to the north ledge as possible (do as I do in the video). Make your way up to the roof and proceed as usual. After blowing up the heli, make your way back to where you landed the helicopter.
Does this strat allow you to complete the mission faster than ever before? No, but having the heli waiting around the corner will save you close to a minute if you plan to go straight to "To Live and Die in Alderney" after completing "Trespass". By the way, during To Live and Die in Alderney, driving an average or better car straight to the mansion, bypassing the heli at the pad, is a few seconds faster with a really good drive. The timer starts and ends when I reach the marker in each video (the video over "old" is my current Classic% pb [5:37:12])
The old strat has 1 extra phone call before picking up the next mission. It also wastes time picking up a helicopter after that altough direct driving would be faster. But even if you'd wait for the call and do the faster driving, the new strat is a 30-40 sec gain!
