A number of minor problems turned up during the prototype phase, and were dealt with over the next year. To improve power the design was updated to mount the newer C36 version of the K14-III. However this engine was slightly heavier than the C32, which required the rear fuselage to be stretched to move the center of gravity back into the proper position. The extra space in the fuselage allowed the fuel tanks to be increased in volume by 455 l (100 imp gallons). The wing was also enlarged and the tail was revised to eliminate the bracing struts.