Several variants on the Hamilcar Mark I were planned, although only one was actually produced. The Hamilcar Mark X, also known as the GAL. 58, was designed to specification X 4/44 in an attempt to allow Hamilcars to be used in the tropical climate of the Pacific, where high temperatures and the high altitudes of many airfields reduced the efficiency of piston-engined aircraft. This meant that Halifax bombers could not tow Hamilcars without a drastically reduced fuel load, which in turn narrowed the range of the Hamilcar. Two initial solutions were proposed to correct this problem; the first was to convert a Hamilcar into a rocket-assisted take off (RATO) aircraft. Two steel cylinders filled with twenty-four three-inch rockets were attached to either side of the glider to provide it with 20,000 lbs of mean thrust as it took off; they would then be jettisoned once the glider was airborne. Initial trials conducted in January 1943 proved to be successful, but was not pursued any further for unknown reasons. The second solution was double towing, where two Halifax aircraft, one stripped of all unnecessary equipment, attached tow ropes to a Hamilcar and then took off from an airfield; once airborne the normal Halifax would then detach its towrope and land, and the modified Halifax would tow the glider to its destination. However, this idea went no further than initial trials in England, as it was considered to be a high risk operation with a high probability of a serious accident occurring. As such, a powered version of the Hamilcar, the Mark X, was decided upon, as it offered the possibility of long-range airborne operations and the ability to retrieve the glider once it had been used. The decision was taken to start developing the Mark X in November 1943 when the potential for airborne operations against Japan itself began to be considered by the Allies; however, for some reason a relaxed view was taken to the development of the production models, and the first was not available until the early months of 1945.