Here’s a view of the forward superstructure where the Vickers quad machine guns were placed. As you can see, the structure near these guns is open and show some signs of rearranging the bridge to get them open. A support pillar is almost certainly present, as is the case with the aft Vickers machine guns. I used my newly acquired drill press to drill in the bridge part and added the pedestal to the gun. It can be added fully painted without having to worry too much about masking. It also gives the gun a small handle while paining them. Two ammo lockers are present per gun, although I have no photographic confirmation.
Photographs of the aft Vickers emplacements show that only a single ammo locker was added to the gun platform, so adding two is definitely wrong. This is confirmed by images of wreck debris where one pedestal was found upside down with only one ammo locker. Note in the right half that a small ladder is present and that only a very low single-bar railing is present. So, where is the second locker?
I think—judging from these two photographs from the offical HMS Hood site—the second locker is simply stored on deck.
The emplacements were made using lathe, as the pedestals are small tubes that hold both the guns and fit nicely onto the deck part (The gun is not glued into position). Of course, while writing this blog post I noticed that the locker on deck level for the port side gun was not fitted snugly against the pedestal as on the starboard mount, but some distance to toward the ship center. Ah well.