Does matching impedance connectors matter in non-RF signals? Why?
15 ns rise time and assumming a prop time of 2 ns/foot gives us a distance of 7.5 feet for the rise time, sometimes referred to as the spacial extent of the edge.  Rule of thumb that many designers use is that you can ignore impedance discontinuities if they are less than 10% of the spacial extent of the edge. So 10% x 7.5 feet = 0.75 feet = 9 inches.  This means that if the electrical length of the connector is less than 9 inches, you can ignore it for purposes of your 15 ns rise time interface.