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.
happy hunting!