So I decided to make a maple truss rod cover to match my veneered headstock. I made a rough template out of paper that covered the general length and width dimensions.
I cut 3 pieces approximately the size of the template making sure that the grain went long ways on 2 and transversely on the last one. I sandwiched the transverse one between the first two, glued them up and clamped the lot between some blocks. I waited a few hours and had a peak. They seemed to be stuck together pretty solidly so I lined up the paper template and drew around it, then cut out the shape with some tough scissors. I then spent ridiculously too long tweaking the shape with 180 then finally 400 grade sandpaper. Once happy I marked then drilled the holes on my Dremel drill press with a 2mm bit. I noticed that one of the layers hadn't glued properly at a corner so I worked some glue in with a scalpel tip then screwed it down to a flat block of wood for a couple more hours to dry.
Then the tricky bit... making it fit. In this state the 3 flimsy veneers became quite tough and I feared that bending the stiff TR cover to the headstock contour might snap it - I proceeded with maximum caution. I put the tip screw in first and bit by bit started clamping my way down the TR cover until I reached the sort of apex of the curve then sent the remaining 2 screws home. Once I was happy that they were all tight I held my breath, bit the bullet and removed the clamp. And Ta-dah it worked.... a matching truss rod cover for my maple veneered headstock.
Just need to lacquer it now.