Yes, there is a post where a wood block with bolts protruding was glassed to the hull. The block was 3/8" thinner than the space between the hull and the slot for the chain plate. 3M-52,000,000 to the hull and generously glassed over. Be careful that the bolts are only proud enough from the block to get full thread engagement of the nut. Otherwise you may not be able to get the chain plate on the studs after you put it through the deck.
As for changing to single lowers, I can only suggest you talk to a very reputable rigger or a Naval Arc. Stuck in a squall is not when you want to discover why Carl called for forward and aft lowers.