Ok, are you talking about the Unity "native" VR there? I thought that Oculus 0.7 was the first to use that.
Our project needs to run on hardware that doesn't support Unity native VR, so we're tied to the older style Unity/Oculus integration. I've found that you can create a profile and modify the Oculus IPD, but it only lets you go as low as 55mm. If you're prepared to hack the Oculus integration C# scripts, it's possible to override the IPD to be 40mm, but even that doesn't seem to give the desired result.
I've also looked into the newer Leap/Unity/Oculus 0.7 C# scripts and noticed that the "Camera Alignment" feature is applying a (40mm / 64mm) rescaling factor to the virtual cameras and then a counter-scale to the child Leap hand controller. It seems that the end result of this is just to move the virtual cameras to be 40mm apart to match the Leap's IPD, but perhaps I'm missing something.