BlameItOnGod13 
basically what i want to fill you guys in on is what area of a vehicle you should be targeting to get the most out of each rocket. in every situation make sure your are not at an angle when you fire otherwise your shot will do usual damage.
MBT - get dat booty. it will immobilize a tank (40-45% or so damage) in one hit when done properly.
IFV - IFV's take the same damage on every side (33-38% i think). i normally try to aim for the turret.
Fast Attack Craft - aim for the back of the boat where the mini-gun's and repairmen sit.
Heavy Transport - aim for the engine (front) i believe. i may be mistaken but pretty sure that's the area and it's a 2 shot.
RHIB boats - aim for the back by the motor.
all Transport Choppers and other Transport Vehicles are a 2 shot, normally. all Attack/Scout Choppers are a 1 shot.
if none of this is helping you then the angle your at when you fire your RPG is wrong.
