I hope it works out well for you gents. Only other offering I really could put forward on it Geophro is to place the random chipping in the areas it would happen. What I mean by that is that an access hatch would not have chipping all the way around it. It would have it around the base of the hinges, closing latch, the areas that one would slap down on to help snug it closed, ect. That is why your eyes are fighting you on it. Your brain knows something looks amiss on it. Look at a couple of period photos of any aircraft with those type of access hatches. The things you are looking for will jump right out at'cha.
Hope that helps. I look forward to seeing it.
ReDhAwK