From
http://modernfirearms.net/en/machine...vickers-5-eng/
It can be seen that the body of the Mk V .5 is basically the same dimensions as the Mk I and Mk III (Naval), but without the tripod mounting lugs, so measurements can be taken off the Naval version, and building it with a flat "bottom". The cooling jacket also appears the same. The pistol grip has minor differences to the Mk XXI Tank, but also a lot of similarities, so that detail can be copied as well.
Some good reading by Forum member Tony Williams
HERE