10. No the picture's not sideways, the cowl is merely stood on its end on the bench. Here we're grinding the welds down, leaving the "step."
11. The cowl was now clamped to the bench while the welds were finish-dressed and sanded with 220-grit on a DA palm sander.
12. With the recess made, now we had to trim the cover to fit. We started by laying 1-inch masking tape around the perimeter, its inside edge aligned with the bottom edge of the "step."
13. With the cover laid in place, more tape was laid on top of the first, their outside edges aligned. This now told us that cutting along the inside edge of the tape on the cover would mean it'd fit perfectly in the recess.
14. One-inch tape won't bend around tight radii without bunching up on the inside edge, so more fine line tape was used before the edges were trimmed and filed to fit.
15. Now to mount the cover: we used Dzus-style 1/4-turn fasteners available from Speedway Motors. Again, 1-inch tape was used to mark a consistent 1-inch distance inboard of the "step," then we cheated and used a mounting tab to mark the locations of the mounting holes on our panel.
16. All the fastener locations were marked equidistant from each other, before each hole's location was marked with an automatic center punch. The centers of the large holes were then drilled with a 1/16-inch drill.
17. The cover was then clamped in place, ensuring it was perfectly centered in the recess...
18. ...prior to being flipped over and the 1/16-inch drill being used through the pilot holes we'd just drilled in the cowl to denote the centers of the mounting holes on the cover.
19. Why did we use a 1/16-inch drill? Because it's small enough that the locating point on the 3/8-inch Rotobroach used to drill the fastener holes will locate in it without falling through. Note the edges of the panel were beveled with a file.