The Mk. II prototype L4250 was fitted with a twin-tail during the tests of the 40mm turret system:
According to exchanges reproduced in
21st Profile Vol. 1, no. 5, Rolls-Royce suggested fitting the Griffon in place of the Bristol Hercules 7.S.M., the Ministry disagreed and Vickers sided with them. The max. speed increase would only have been 12 mph, from 248 to 260 mph, at the expense of 790 lbs increase in weight and a 110 gallon decrease in available fuel.
Range at max speed would drop from 1630 miles to 1150, and at a cruise speed of 180 mph (same for both engine types), from 1970 to 1620 miles.