One of the members here (growler) has a crf kitty and has excellent information in her thread here:
http://www.pets.ca/forum/showthread....horus+cat+food
She is usually logged on every night around 8:00pm pacific time and will be more than happy to give you more advice. Sugarcatmom is also another cat guru here and has extensive information as well.
Growler's cat Duffy is 16 years old and has been living with crf for over a year and is doing very well with the excellent care received from her mom.
Good luck with your kitty.