What about making another forest Limited to a second camera that is facing backwards.
If its an animated camera then you have a more challenging time of reflecting the Main cameras motion
off the top of my head you could duplicate your original camera and link it to a dummy that is at the centre of your reflecting object (and rotated to match).. link a new camera (the one that is limiting you reflection forest) the the duplicated main camera, then scale the controlling dummy in a way that mirrors you MAIN camera.
Its a bit convoluted though, so personally, i would use a reflection card that has a texture on it.. maybe put a few hero objest in front of it, if you really need some parallax shift.
If it works, the easiest way is definitely adjust the back offset, like mentioned above.