Unity Shader Stream Output Stage

Do Unity 5 shaders have access to the stream output stage in the DX11 pipeline? Reference: https://msdn.microsoft.com/en-us/library/windows/desktop/bb205121%28v=vs.85%29.aspx

I want to compute new vert data in the shader and then output this information to a script for non rendering purposes.

I am currently using a GPGPU shader to achieve this, however the load on the pipeline during return is not desirable. This can't really change as it is proportionate to the number of verts in the mesh, so I figure that if I could use the stream output stage in the DX11 render pipeline which Unity uses then this could mitigate such load as the vert data will only need to be passed to the GPU once during the rendering stage, instead of twice.

Is this methodology correct and can I access the stream output stage?