I have decided to give a shot at that informant challenge I made a while ago. For those who can't remember it you basically have to kill each target in high profile, making it much harder. For the stunts I do in this challange can be just as complex as AC2 and ACB, I had to do a lot of planning for this, and as a bonus I try not to startle the crowd at all.
Before you start, collect a flag close to the informant so if you stuff up you can either jump off the edge into the water or kill 3 civilians and respawn close by. Try not to kill the stationary guards before you collect the flag, makes it too easy.
To use the viewpoint for my stunt I have to clear the area of those 3 stationary guards. The next problem is that both the normal patrols and the target will inspect their bodies, making the whole area messy. This is why I run away, running a certain distance gets rid of the bodies (and also gives me something to do while I wait for the target to get into place)
On the way back to the view point I kill the 2 guards to draw attention to that area. This way once I do the stunt and kill him, random patrols are less likely to stumble along as they are all in the area where I killed those two guards.
As for the stunt, I lock on to make it more cinematic. Wait until he crosses the shadow between those two trees and jump.