I tried this, but eventually settled on a completely grain free dry. My cats sorta liked it, but it was hard to tell as I was switching dry food quite a bit.
The email I received from Shelly of Castor and Pollux was very imformative and reassuring. I would still be using their food but decided to use only grain free products.
One thing is that only the canned food is a USDA certified organic product while the dry is not, tho the dry does include a lot organic ingredients. The USDA organic label means some very specific things with respect to percentage of organic vs non-organic.http://www.tilth.org/about/FAQ.html