I have a book of the Mosquito by M.J. Hardy ( ISBN 0 7153 7367 6 )published in 1977. It mentions the 6 pounder gun
on pages 60, 61 and 62. It was used in anger against some U-Boats. It also mentions a 3.7 inch gun being fitted shortly
after the war. The installation weighed 4,000lb and some successful air firings were made before the aircraft was scrapped.
The six pounder with ammunition and supporting bar weighed 1,800lb with the trunnion reaction as high as 8,000lb