Sunderland prototype 37mm COW fitting

It’s said that the prototype Sunderland was designed for a 37mm anti-submarine gun (I assume a Vickers COW).

Was this ever actually carried out? Does anyone have any photos or some idea of what this might have looked like on a Sunderland?

Here’s a nifty video showing it attached and in use on the Blackburn Perth http://www.youtube.com/watch?v=mdsBQjq7fJg