Sas.
Need to go back to flight school. Often vertical lift approach from the side to their spot not down the deck. As to deck spacing their are no amphibs which can take two side by side running 46's next to the island. By deck configuration and geo probably more running V-22's can be fitted on a LHD than 46's.
As to the high altitude capability of the UH-60 only this needs to be considered (and carrying only four crew):
Looks like a prequel to Abbotabad except they had only a few feet to fall.
The Sultan