Can 2 displacements be rendered?

Hello,

In my object, half of it is material 1, and the other half is material 2 
(selected faces.
there are UVW maps and different material id channels for each material or 
selection.

Material 1 and 2 have different displacement maps.

when I try to render in MR, only the textures render but not the displacement 
maps. what am i doing wrong? all the mat channels are set. Can MR render 
two displacements on one object?

thx, alex