You had me confused for a bit with the glass on the outside of the body, but I think I maybe I understand. You used the body as a form, laid a panel on the outside to get the contour and thickness you needed, then drilled a 1/4" locator hole through both. The new internal piece got a smaller hole for the neck, and flattened out some to give the mounting surface you needed, and then was glassed/glued inside the body after drilling the 4" hole in the body. Is that right? I really like the way it turned out, and I kind of wish I had done something like that for mine to eliminate opening the trunk to fuel up.