I'd add that supporting the entire mass of the pistol by the barrel, subjecting it to the shock and vibrations of a moving vehicle can't be good for accuracy or reliability.
I'd be a little concerned about the gun bouncing around on the rod. Also appears in the second picture it could result in your finger getting directed on to the trigger. I'd pass on this for a vehicle.
I would take a look at the G-Code RTI wheel. Just mount it where you want and attach the hanger to the holder of your choice or use a G-Code holster with the RTI option installed already. This way you can throw a belt-based RTI wheel system in your glove box and go from vehicle to waist without having to unholster the firearm.