I did exactly that. We don't have a spinnaker on our Catalina 42 but I did want a whisker pole. Found some aluminum pipe that was the right OD but the walls were a bit too thick to fit the standard pole ends (from Forespar I think). A few minutes' work with a rotary rasp in a drill was enough the enlarge the ID a few thousandths so the ends fit. It is a little heavier than the specified tubing but heck for stout and the pipe was about 1/2 the cost of the tubing.