high protein cat foods and FLUTD

[marine's girlie]

hi everybody,
i'd like to put my cats onto a high protein cat food like EVO, but i'm concerned about the ash content. i find ash of 9-10% in all the foods and i know that in order to have a high protein food, a lot of meat is required and that ash (mineral content) is proportionate to the meat content. since i haven't heard of these types of diets leading to an increased incidence of crystaluria and blockage, i'm wondering why.
i hypothesize that it may have to do with the urinary pH which is produced by such a high protein diet (ie one that it is much lower than other foods) which precludes the precipitation of triple ammonium phosphate crystals in the urine. i certainly haven't head of the newer prescription diabetic feline diets causing this problem, and they are based on the same high protein principle.
or maybe foods like this are just so new that no links have been drawn.
does anybody else have any other ideas?
i have found evidence that high protein diets can prevent struvite formation, but i have yet to come across anyone with anicdotal evidence which supports this.