I understand that this thread isn't about the Airflow fairing - but as someone who rode a Crusader fitted with one in the 1960's I can say that they looked far better than you'd think when fitted to a brand new Crusader (I realise that this is a time-related assessment - I mean we'd not seen the sleek things that came later).
Also its weather protection was legendary. In use it made litter difference to the speed of the bike - one up or two up. Far better from that point of view than the Avon touring fairing. Weather protection as good if not better than the Ariel Leader!
I know looking back from here these bikes seem quirky and hopelessly unglamorous - but in their time they were fine machines - Ariel 250's and the Crusader in all its forms were by far the best of the British 250's of their times.
Then came Yamaha and Suzuki and Honda - but none offered bikes to fill that 250 tourer gap. And no one ever has - maybe except the T10 Suzuki. Oh dear - nostalgia creeping in - time for a cup of tea!