ambient occlusion + forward cutout shader on deffered lighting

Im making stylized tree for my game. I use many light sources so Im using deffered lighting system. Best visual result is with using light attenuation node. It can only be used in forward shader. My problem with this combination is ambient occlusion. I see it through my tree. I currently use unity post processing stack. The problem can be solved by using "ambient only" checker, but the visuals are poor then.
I tried to use any other AO plugin, same results. The only way it worked was HBAO with normal reconstruct option, but it decreased my performance by 20%.

The screen is below, I increased some contrast to make it more visible.