easy rendering for Rhino in Windows
Not sure of the best way to do it in Rhino but you can acheive pretty convincing object reflections in Photoshop.
Basically you select the object you want to reflect,
paste it (so it is on its own layer),
now select the new layer it is on and bring its transparency down a little
now go to the transform tools (under edit I think), now you can turn it upside down and distort it to look like the reflection
then bring down the transparency on that layer until your happy with its strength.
Hope that helps if you don't get answers you need to do it in Rhino.
I had a similar problem where I had put a "covered structure" in a playground scene and I could not get shadows to fall on the bitmap, ended up "faking" the shadows in PS.