I am borderline on suggesting for you to use an I-20 rotor for throwing 25 - 30 feet. You should use a rotor that is designed for that small of throw, Hunter PGM rotor or Rain Bird 3500 series or 5004 series rotor. The I-20 would have to be turned down a lot which could mess up the uniformity of spray (unless you use special low angle short distance nozzles). You can use the I-20 if you use their low angle short radius nozzle, however, you will need to request the special nozzles when you order the I-20 rotor. I think the I-20 is built higher quality and has more features than the Rain Bird rotors mentioned above, however, all these rotors are of very high quality. Your choice...
For more on radius and arc adjustments see the following link on our website for the I-20 rotor:
http://www.sprinklerwarehouse.com/manuals/I-20install.htm