I stand corrected as I found some numbers off the internet and I take yours from a published source as correct.Hi,
the belt of Littorio's was 4.4 meters high, extending for 2 meters under water at normal battle load (source: E.Bagnasco, pag 56-58 "Littorio class battleships", Italian edition). It was considered enough for Mediterranean seas and for a ship that did not change much her draught due to her limited range (not much fuel could be embarked anyway).
It's a very small belt, but Bismarck's was 4.8 meters only as well, and the 14" hit from PoW was not able to detonate directly within the vitals (albeit flooding them)
I also am mistaken on the KGV belt as it appears that the figures,also derived from wikipedia, are reversed.
So the corrected values would be .
V. V. mb 4.4 meters in height 2.4 above/2 below the waterline
KGV mb 7.2 meters in height 4.6 above/2.6 below the waterline and for comparison
Bismark 4.8 meters in height 2.6 above/ 2.2 below the waterline
Still a big advantage to the KGV, a much larger protected volume. At longer ranges in its imunity zone the KGV will have a much larger protected volume than the V V . With this plus 10 vs 9 guns, that have more than twice the bursting charge, a long range action favours the KGV. The KGV needs to play the angles right in a closer action.
I wouldn't dismiss low hits so quickly, at Denmark Strait the PoW took 2 hits below its 2.6 meter deep belt , and the Bismark took one hit below its belt 2.2 meter deep belt.