A similar installation was fitted to a Liberator, carried on the bottom of the fuselage almost underneath the cockpit.

Самолёты на фотографии: Aircrafts on the photo: Consolidated B-24 Liberator - СШАUSA - 1939

The MAEE carried out tests on firing RPs from a Sunderland III and reported on this in October 1943.
A rack similar to that fitted on a Liberator was attached to JM681. It was slung on either side of the hull aft of the forward entry door with a baffle plate immediately below the wing root loading point. The rocket rails were about five feet above the waterline when the aircraft was at rest. This proved a rigid firing platform and proved satisfactory, with no signs of distortion. Loading rockets from a Woolston dinghy was fairly easy.
Four pairs were fired while waterborne, followed by 160 in the air. A full salvo of eight RPs caused some rivets to pop out and the fire extinguisher and IFF stand inside the hull came loose. The rear porthole on the port side of the galley twice blew out. There was much less damage when the bombs were run out.
Apart from these minor points, the installation was judged to be satisfactory for operational use.

Самолёты на фотографии: Aircrafts on the photo: Short Sunderland / S.25 - ВеликобританияUnited Kingdom - 1937