Larry, if you want to safely go much higher than 12 feet, plan on getting a fourth stick.
Lonewolf says the steps are 15" apart, so a 3 step stick is good for 30", or 2.5 ft. Figure in 18", 1.5 ft, for the first step and between sticks. Add it up for 3 sticks and you will get 12 ft. A little more arithmetic will tell you that to get to 16 ft, it will take 2.83 ft for the first step and between sticks. That is a LONG stretch, almost 3 feet, and I know that I'm not gonna make it. 12 ft is also about the max I can get with my 3 Rapid Rails, which is why I'm adding a fourth long section.