Nearest clip plane for light beams with Volumetric Fog

Trying to reduce the diameter of the start of my volumetric rays. You can see in the attached that my Volumetric Fog Start Distance is zero. Also using a low Scattering Distribution to maximize density at perpendicular camera angles. I need to have the light beam precisely match the smaller projection lens element.
Is there some console variable that would help? Seems like the beginning is being clipped somehow.