The early SE-5's had a sort of canopy that surrounded the front of the cockpit, but was open at the rear. Pilots didn't like it either, so it wasn't installed thereafter.
This was known as the 'Greenhouse' and distorted pilots' view through it and 56 Sqn, the first unit to use the SE.5 had the greenhouse removed and its aircraft fitted with flat plate windscreens robbed from Avro trainers. In the SE.5a, the first prototype of which was the third prototype SE.5 A4563, had a lowered seat and faired headrest and the 'Avro' style windscreen.
It should also be mentioned that the SE.4 never flew with its moulded celluloid canopy as no pilot wanted to fly it with it fitted!