Get my Image Effect to run after Post process

Is there a way to get my custom Image Effect which uses OnRenderImage to happen after the Post Process stack has been rendered, I have tried changing the Script Execution order but it has no effect, is there some trick to allow this to work.

Also is it possible to save the depth buffer from one camera and use it as a texture in an image effect shader on another camera?

 

I have done this previously, you need to render it into a new RT with a custom depth-copy shader and pass that RT to the other camera. That is the only platform-agnostic method that will actually work reliably. Just be careful about what type of RT you use, as obviously depth is typically very high precision.