About this detail of the Tiger
The Tiger's exhaust was designed, at first, with a flapper valve to permit submersion. Later, a protective disc was added, suspended above the valve by 5 legs. The Tunisian Tigers did not have the disc.
Rye Field's "Tunisian" model is in error here. It provides the protective disc (D27) and tells you to install it above the valve. You should not use part D27 on a Tunisian Tiger. Unfortunately, the valve base (D55) has 5 holes for the legs of D27; these holes should not be present.
Another problem with part D55 is that it shows the valve closed, as if the Tiger were prepared for underwater travel. The valve would normally be locked open, as this photo shows.