Ok so I just looked into this, and you may be able to replace the Distance field with a Custom Mesh…It doesn’t appear that increasing resolution helps…which I didn’t really expect it would
If you really wanted, you could turn Distance Fields off by setting the Resolution to 0 but then you wouldn’t receive any shadows from that surface.
Note: You’ll have to increase Indirect Lighting on your Directional Light to get the Interiors brighter.