It's probablyperfectly safe and sane to run 45 psi, that 55 psi minimum probably has to factor in the safety and likelihood of someone weighing more than you. Really you just run the risk of a sharp edge giving you a pinch flat, and it depends completely on the course, some courses might have more rocks and pavement than others. Personally I weigh more than you and I've run 45 psi on thinner tires for certain races. It all depends.
You could even borrow a set of wheels and tires, and keep them in the pit in the event you do get a flat, that's pretty common practice for a cross race.