haha thanks for the advice. If you figure out how to do that in maya don't tell the foundry!
matching the render to the backplate is generally done in compositing programs like nuke, shake, after effects, combustion etc etc. Which is why you ought to render things in passes. using programs like this give you more control than rendering things straight from maya.
Its a bit like when people render out occlusion renders. These are passes that are used to control parts of the 3D element. In the case of ambient occlusion you can adjust contact shadows.
if i were to render a diffuse pass and a reflection pass, i would add the reflection over the diffuse and then be able to control the look of the reflections.
Ill show you in my next post.
the movie has just finished.