Yes but the OP is talking about trying his 25/28mm (what is this weird Spesh sizing convention anyway) tires as low as 75-80 psi, for an approx. 250lb rider+bike setup. When the various online tire-pressure calculators are saying that a 15% drop would be obtained with a pressure of approx 105-115 (depending if you use 25mm or 28mm in the calculator), and whether or not 80psi is within the range stamped on the side of the tire(s), it seems very strange to me that "feel" is driving the bus in decision making on this.