[4] He briefed the British War Cabinet in March 1918 on what he considered to be the merits of the design (high power on low weight), and indicated it was the first engine on which 'it might be advisable to standardise', even though it had not been fully tested.

[5] With Weir's backing, orders for 11,500 engines were placed from 13 suppliers by June 1918, but in the same month the Royal Air Force (RAF)'s Technical Department admitted that complete drawings were unavailable as the design was still not finalised.

The copper-plated cooling fins proved useless; the cylinder heads tended to glow a dull red at operational speeds, and in extreme cases caused heat damage and even charring to the propeller.

Attempts to improve cooling with cylinder redesign were marginally successful, but the death blow fell when it was realized that the engine was designed to run at the torsional resonance frequency of its own crankshaft, causing severe vibration, a little known condition at the time.

Gunston's observations suggested that it had been as well that the Armistice had been signed in 1918, as the only other aero engine still in production at that time was the Rolls-Royce Eagle; all other types having been cancelled in favour of the untested Dragonfly.