Original sentence: The second prototype incorporated cut-outs in the lower wing roots which had been introduced to increase a pilot's downward vision while subsequent modifications to this and the other two prototypes were made to the radiator, upper fuselage decking and vertical stabilizer
Edited sentence: Neither of these features proved successful, and they were deleted from subsequent prototypes.The last two prototypes featured numerous modifications to the radiator, upper fuselage decking, and vertical stabilizer.The lower wing roots featured large cut-outs to improve the pilot's downward vision.The second prototype introduced upper wing radiators in place of the frontal radiator