I'm going through this at the moment. (thread here: [url=] http://forum.champdogs.co.uk/topic_show.pl?tid=148093%5b/url%5d
includes suggestions from other forum members)
My 4-year-old male developed struvite crystals (they hadn't gone as far as stones luckily). He was previously fed one raw meal and one kibble meal a day. Our vet advised the Royal Canin urinary diet to dissolve the crystals. It took three and a half months for the crystals to dissolve completely.
I have been checking the pH of his urine weekly: it reduced quickly from 7.0 to 6.0 and remained more or less steady with an occasional dip to 5.0. An early raw bone pushed it back to 7.0, but it quickly dropped again and his raw Christmas breakfasts did not disturb it.
He stayed on the RC kibble for another week and then began to introduce the raw food again, first as a topping, (pH 6.0) then as one meal a day, at the end of that week the pH was 6.5. The next week he had raw for both meals and the recording at the beginning of this week was 7.0. I put him straight back on the Urinary diet, and will test again on Monday. At present I am recording the food he has and trying to keep him on the same for a week at a time. I am also currently trying a green vegetable supplement from Dorwest which they say may help keep the urine pH right. My aim is to return him to at least one raw meal and hopefully two while remaining acidic and crystal-free.
Sorry for the essay, but hope this helps a bit.