The Tiger had large air inlet grilles on its rear deck, either side of the engine hatch. Below each grille, a metal duct guided the air to a radiator.
Each duct was permanently attached to the underside of its grille, and almost invisible from outside the tank.
Border's kit provides you with the ducts, each one made from four parts. But then, Border tell you that the ducts are optional "accessories". They're not.
Border tell you to put the ducts on top of the deck (image from Border's instructions). This is absolutely wrong. Border warn you that the turret toolbox won't fit if you do this. Well, of course, because nobody ever did it!
To build your kit correctly, ignore what Border tell you. Attach the ducts to the bottom of the decking; they should fit into the triangular space above the fuel tanks, when the roof is placed upon the hull.