I removed the fenders today.  I want to undercoat them because they didn’t get painted when the previous owner had the car painted.  Not sure why they didn’t get done (they were off the car when the car was painted).  Even if it had been painted,  I’d still want to put a very light/thin layer of chip guard undercoating on the undersides of the fenders.  It’ll actually help protect the topsides of the fenders from getting little star cracks in the paint when rocks from the tires hit the undersides of the fenders.  Maybe the previous owner had the same idea in mind, thus he didn’t see a need to paint the undersides.  Here are some pics with the fenders removed…