Hey, Doc.
I've read those studies too, and you are absolutely correct that the 5-10" height creates a healthier grass plant for cool season pasture grasses. However, most folks growing cool-season ornamental grasses (fescues, etc.) will benefit form cutting between 3 1/2 - 5" . This especially applies to Tall-type fescues that are not rhizomatous (sp). That is, the fesuces that propagate only by seed and mature into clumps.
When most tall-type fescues experience competition, they will display a finer grass blade and the stand will remain thicker. The only way to accomplish this with tall-type fescues is to routinely overseed and keep the established grass height between 3-5" so that individual grass plants do not become dominant (in clumps). Once tall fescue gets tall and clumpy, the blade become more course, "good" competition drops off, weed seeds find purchase, etc. Ultimately, a clump of fescue is more resilient than a plant tighter stand, but it looks worse and more soil is exposed. Fescue is naturally adept at tolerating drought because it goes in and out of dormancy so easily. Even the tighter stand recovers quickly. Having said all that, cutting fescue any shorter than 3" does, in fact, create a more shallow root system. So, the sweet spot is where the root system grows deeply, the stand stays fairly thick, and the lawn looks pretty. A taller grass will withstand grazing and rough cutting better than a shorter grass, which is the objective in pature grass applications.
I cut my K31 fescue lawn at 3 1/2 inches until June rolls around, then up to 4" over the summer. Once October comes, I go back down to 3 1/2. I aerate and overseed thin spots each Fall. Also, I apply 70% of my fertilizer in the Fall and only pre-emergent/light fertilizer combos in the Spring.
As far as organic fertilizer, alfalfa pellets are great. Some folks claim corn gluten meal (not corn meal) provides good nutrition and has a pre-emergent action when applied in the Spring. Applying compost is often touted, but, unless you have the ability to build your own compost, it's pretty expensive to buy and tough to spread unless you have a small manure spreader.
Warm season grasses are often advised to be cut shorter. Bermuda, Bent, etc. do well under 2 1/2 inches or even shorter. Most finish mowers cut at heights only up to 4-5". I'd say cut it as high as your can and still satisfy your cosmetic preferences.
