G-ADDR, the fifth Scion II, was retained by Shorts as an experimental testbed aircraft, and it was on this aircraft (temporarily designated M.3) that a scale wooden model of the slender wings (with Gouge flaps) for the later Empire boats was tested, the first flight in this configuration being conducted by Lankester Parker on 6 August 1935. With these flaps fitted it was tested at the Royal Aircraft Establishment, which found that the Gouge flap decreased distance to take-off and stalling speed, among other improvements. Further work with standard wings was carried out; one flight from Rochester Airport, with experimental full-span flaps incorporating retractable spoilers instead of ailerons, was made on 22 July 1936; this idea proved unworkable, Lankester Parker having to draw on his considerable experience to coax the aircraft around on a single circuit before landing safely. The standard wing was refitted and the aircraft continued with Shorts in this configuration until it was impressed into military service in 1940, an operational usage experienced by 14 of the 22 Scion/Scion II aircraft.