Uffa Fox had started work on his ideas for other versions of an Airborne Lifeboat immediately the Mark I was designed and probably before. The Air Ministry invited tenders from many boatbuilding companies for new designs and construction methods. Designs from Uffa Fox, Aldous Successors (Brightlingsea), The British Power Boat Company of Hythe, The Itchenor Shipyard, Vosper and Wates were reviewed at the end of 1943. ‘Rescue From the Skies’ lists many of the comments on these designs.
Part of this design-review process included different construction methods. Uffa had proposed two options, one normally planked and the other for moulded plywood. Other designs suggested plywood including chined hulls in plywood (rejected for aerodynamic reasons).
Uffa Fox is credited with the adopted design which included many features from the different designs and from suggestions of the review panel.