From what I've seen, most of the shaders are basically set up the same way, very simplistic, and very easy to convert to PBR.  P11 doesn't have a PrincipledBsdf node, so the next best solution is to use the PhysicalSurface node without going completely into Cycles (my preference).  This is the rudimentary change I made to some of the material in the render field of view.  I just noticed that the Roughness channel should be slightly higher and the Metallic channel increased to around 0.8 to give the material some reflective properties.  

Keep in mind, that if you use Superfly rendering, just about every surface in your scene should reflect some degree of light to help brighten up the surroundings.  Next time you watch a movie with a nighttime outdoors scene, observe the ground, it is always wet with water, a highly reflective medium.