The question I have are why does the F4U-1C have less hard points on it's wings 4 instead of 6.
I think I might have it figured.
F4U-1D normal loaded weight: 12175lbs
F4U-1C normal loaded weight: 12470lbs
Difference is 295lbs of extra weight, placed on the wings.
5" HVAR weight: 140lbs
Take away the ability to carry 2 HVAR's and you take away a load of 280lbs from the wing, meaning that the maximum possible load on the wing stays about the same as the F4U-1D.
Navy doesn't have to do any testing to see if the wing could safely take the extra weight with a maximum loadout on the F4U-1C.