I'm assuming you don't want to cut two holes in your hulls so the other option (assuming you already have the ports installed) is to open the port on a hot day, cover the hulls with black trash bags and bake the moisture out.
The H18 comes stock with one access port in each hull. He said he was adding another, so that would mean he will have two ports in each hull.
I agree, you should pop the ports open and vent the hulls. Use a small fan to keep air circulating (does not need to be a high velocity/volume fan, just something to keep pumping fresh air through the hulls). Close the boat up on rainy days and pop it open on clear dry days (like after a cold front passes).
If the foam is waterlogged, I would definintely be concerned about delam, not to mention the added weight.