The PV-2 Harpoon is very similar to the Hudson.....When the PV-2 operators converted them to sprayers and tankers, the first to go was the turrets, all the associated equipment and armor plate...To counter this loss, just add sand bags.....engine blocks...sacks of concrete....etc.
My PV was converted by the Navy to a PV-2T2....some type of radar trainer, where the turret was just in the way...so it was removed, and a large alum. cover plate/patch was added to the upper fuselage....They left the thicker skins fore and aft of the turret, on top the fuselage..blast shields for the .50's....and in the tail, added lead weights...I believe that these are probably the original weights that the Navy installed on this bird....they are at the bottom of the inverted "V" brace, and there are two of them...one on each side of the brace....

Hope this helps,
Gary