I'm not a structural engineer, but I don't think the ports weaken the hulls at all. I installed them in a perfectly good set of H16 hulls and was glad that I did. It really aids in drying out the interiors. If your boat has had much water sitting in it without draining, chances are that the Styrofoam flotation is waterlogged and you are hauling around 10 extra pounds with that. Another bonus with the ports is that you can hang a catbag in them and have some nice storage. It takes less than an hour to install a set and it can be done with minimum tools.
Jack