The F4U-1 carried 177 lbs worth of fuel tanks and their protection. The deflection plate was at 25 lbs, 53 lbs was pilots back armor. The bullet proof glass was also there. None of these were aboar of XF4U-1? The 'armament provision' (cradles, heaters, etc) was at 365 lbs, at what we add 1000 lbs worth of guns and ammo (6 x 400 rds). The XF4U-1 is at maybe 120 + 300 lbs for that, wing guns only?
The LMGs and their ammo were worth 125 lbs, per pdf posted above. Along with deletion of wing bombs, we save there 330 lbs total - enough for additional pair of .50s. The B series engine should give enough of extra oomph, to cater for extra protection, but as always, Corsair's pilots are best advised not to play the lightweight fighters game.
edit: the term 'armament provision' might also include armor installed??