About this detail of the Tiger
In the Hachette Tiger Tank kit, the vision ports in the sides of the turret have openings that are too large. You can see them in this modeller's blog.
In a real Tiger, these vision ports consisted of a steel plug with a narrow slit, backed by a removable block with 90mm thickness of glass.
This badly preserved "Late" Tiger has lost its Zimmerit coating, allowing us to see the shape of the plug (with impact damage at the top). The slit is wider and thinner than Hachette's version; in fact it's only 9mm high. Note that it lies slightly below the center of the plug.
This is a profile through the plug and the turret wall of the Tiger. You can see that the slit is slanted downwards; its inner end is at the center of the plug. The block containing the glass was removable, and it was a standard part used in other German tanks. Spare blocks were carried inside the Tiger. (This diagram uses a green tint to show the location of the glass.)
You could improve the Hachette Tiger's accuracy by filling and re-opening the slit, taking care to keep it slightly below the center of the plug. With the Zimmerit coating, it's not necessary to be very exact.