I would upgrade to a commerical controller if you are going with that many zones. I would suggest the Hunter ICC controller. The ICC can handle up to 32 zones, with 4 different programs and up to 8 different start times. You can easily add a rain sensor or a remote control to the ICC. go to www.hunterindustries.com - products - controllers - ICC to check out more info on it.
Tony Posey
Ridge Run Landscapes