Right on Kevin!
A "one psi, 1.0 psi", increase in inside hull pressure is a force of 2400 pounds trying to blow the deck off the hull on a 20ft hull. Example: 20ft x 12ins/ft x 10ins average deck width x 1.0 psid = 2400 pounds. That is 1.2 tons!
Be very, very careful.
Bill