Metal din-rail is mounted inside a control panel but it they are using 1" long/high PVC to raise the din rail off of the backpanel. Machine screws are used to secure everything.
Grounding terminals are mounted to the dinrail.
I thought there was some kind of a NEC clause that required metal-to-metal contact and not just depending on the screw threads, wouldn't be the first time I've been wrong.
Please don't derail this thread talking about UL.
the problem is that it is really a UL issue and not a NEC issue.
note how 250.8 is worded. the word "listed" is used several times.
UL allows the bonding connection between the grounding terminals and the DIN rail to be made by the clamp in the grounding terminal that clamps onto the DIN rail. The bonding connection from the DIN rail to the metal of some kind of enclosure is made by the mounting screws that hold the DIN rail in place. These are all things that UL allows.
I am not sure just what spacer arrangement you have but it is not unusual to cut a short piece of tubing and use that as a spacer between the panel/enclosure and the DIN rail and run a long screw through the slots in the DIN rail and into the enclosure/panel. I don't have an issue with that.
if it makes you feel better, you can add a bonding conductor to a grounding terminal on the DIN rail, or to the DIN rail itself. I would point out that it is unlikely that UL has listed the DIN rail to be bonded running a conductor direct to the DIN rail, so that might be a violation if that is the sole bonding means.