I'm using platenuts attachment to the bottom of the cowl. I have seen many hinges on RV's that become loose and wear and after seen good results on an RV 10 using platenuts here, I decided to do the same thing. The bottom cowl does not get removed a lot and this is a good way of locking up the cowl to the plane and keep the entire unit from vibrating and wearing the hinge pins. See picture 3 below of the RV 10 cowl attachemtn on the bottom only.
