Had some time to work on this more -- today I focused mostly on adding the multiple reflection bands. I didn't understand what was causing them in the reference images, until I realized that retroreflected light from the grazing angles of the cone still had to travel through the clear coat layer on its way back to the camera, and that could possibly cause additional highlight bands. Some additional renders with maps from HDRI Haven: To get the left and right bands, I used two more copies of my anisotropic dispersion setup, rotated +-45° on vertical axis. To overcome the black artifacts, I add the two together, since with 90° of difference they don't overlap. Then I blend them in with the original dispersion shader, but only on grazing angles. (Vector and Texture outputs rotate in opposite directions. S_GlossyDispersion is the same setup I was using before, but grouped together so I can make instances easily.) I have no idea if this way of doing it is appropriately imitating what's actually going on in the real material, but it does approximate the look, and I at least tried not to break physicality too badly.