I am pretty sure this hasn't been posted a few people know it so yeah.
You have to do the exploit to get on top of the base not the roof but were you have to wall jump to get there.
On top of (A) base there is a spot on the opposite side of were you get stuck in the invisible walls.
If your facing the (H) base and you followed the step above it is on your back left corner.
Kinda like this
Horde base IGNORE THE DOTTED LINES!!!!!!!!!!!!
|-------------|
|_________|
|-------------- |
|-------------| | < Invis wall
|x_________|
Alliance Base
x is were it would be on the roof
its a small hole that you can fall through to get to any level of the base quick! ill get screenies tommorw hope i helped a little!
Edit: ADDED SCREENSHOTS!
BASE.jpg : Free Image Host.
base 2.jpg : Free Image Host.