Box mapping a heightmap for the displace modifier?

I have used box mapping for the diffuse/glossy etc on one of my models. i.e. in nodes:

Object output of Texture coordinate node plugs into a mapping node, which plugs into an image node with diff/glossy textures set with projection as box (currently posting from phone…pics to follow, if that is not understandable).

I have also added a displacement modifier, but I am having difficulty lining it up with the box mapped textures. Is this even possible?

I have added the displacement modifier, and added a new texture via that panel and called it “DisTex”. In the texture panel I have selected DisTex under the displacement section, set the texture coordinate to local (and tried all the others). However, there doesn’t appear to be a way to select box projection in either that section or in the texture section.

Any ideas?