You need 4 chaffs if you want to cut down on your play time on
Act 4.
1. For the Tank hangar.
2. The place after the the Crying Wolf fight which is the Blast Furnace.
3. The Casting Facility, with patrolling Gekkou and Dwarves.
4. The last stretch to reach REX.
For area
1, you can actually pass it without using any Chaff grenades but a waste of time.
Area
2 is possible as well but also a waste of time.
Area
3 is necessary for me because you will just have to worry bout the Gekkous.
Area
4 is also necessary to not waste time.
I needed 4 chaffs to cut down my play time because I wasted my limited, un-stocked non-lethal bullets on the Beast forms for 2 Acts. So I wasted my time sneaking

Finish the game with 12 minutes to spare. That is why to cut down time consumed on Act 4 and to avoid detection, 4 chaffs are good for me
This post has been edited by Muchi: Jul 24 2008, 09:22 PM