Some of the RNAS Pups had a modified centre wing structure and wire bracing to accommodate an upward firing Lewis in place of the Vickers for shipborne anti-Zeppelin duties. Some of the Pups retained the Vickers if they were assigned to shore bases and used for anti-Gotha duties. Of the shore based aircraft, some had the cutout covered with transparent material.
Shipborne aircraft also carried flotation bags in the aft fuselage in an attempt to help in recovery when they were ditched (approx 20 min flotation time). Later on, inflatable bags were carried under the wings with a fuselage mounted air bottle. Modifications were also made to the main and tail landing gear to improve the Pups ditching characteristics. This system allowed a Pup to remain afloat for several hours.
The WNW RNAS Pup kit has both types of wings and fuselages for the standard Pup (Type 9901) and the shipborne Pup (Type 9901a). I don't believe it has the later flotation system.
Cheers,
Rich