I can not correctly measure the depth because the outer lip is tapered in and not straight in like yours. That's the major problem. The legs of the base sit on the taper. But i can tell it's not 1/2 inch deep. Not even close. 3/8 at best
With the taper holding the legs out some, can the legs be ground down a touch, in order to get it in?
Just asking, i have not seen one close up and not even sure what it is made of, or how. All i know is someone will have to figure it out, or i will have to stay with the standard gas cap, because my new goodmark fender is tapered in also. I cut the section out of my old fender, which i will probably keep, in case i decide to patch it in their.