Displacement Map and VRay proxy

[trick]

I am a bit confused about displacement maps and VRay proxies.

I always asumed displacement was not supported with VRay proxies. When rendering VRay proxies the displacement map in the VRayMtl is not rendered.
Now I read somewhere in this forum that you CAN render a displacement map if you add a VRayDisplacementMod modifier to the VRay proxy and enable "Use Object MTL". However when trying to do that, the VRay Proxy renders as the reduced (visible viewport) object with one material (matID=1).

I am still using VRay 3.70.01. Now is there a way to render displacement maps on proxies?

[HowardDay]

Did you ever figure this out?

[hermit.crab]

It seems to work on V-Ray 5 with "Use Object Mtl" and a multi/sub-object material. V-Ray 3.7 does not seem to produce an adequate result, however.