I've never seen a mower go to 5 inches. 4 should be fine. 5 would be nice as would 6 up to 9 inches. If you want to talk about tall St Augustine, I'm the guy to talk to. I have a lawn in George West, TX which has not been mowed since October of 2011. In most shady parts it is 32 inches high. Most of the rest is about 12 inches (full sun) but some is not up to 8 inches in all this time. Water conservation is the issue I was addressing by stopping mowing. The parts of the lawn that are up to 32 inches have not been watered in months except for our sparse rainfall. One part has not been watered once since Oct 2011. There is no thatch build up in any St Augustine no matter how high it gets UNLESS you water it every day and fertilize frequently with liquid fertilizers like Medina Hasta-Gro. That combination allows the entire grass plant to develop and survive on top of the soil - roots and all. If you follow our normal mantra of watering deeply once per (week or month) then you won't ever have thatch. Oh also feeding with dry fertilizer goes along with that. Yellow at the tip? When you mow it should not have a tip left? You should have an end that looks like someone sliced it very cleanly with scissors. If it looks raggedy at all, then you need to sharpen the mower. Here's a picture of my tall grass lawn. My dog is about 30 inches high at the tips of her ears. The grass had flopped over from being dry but it never showed any of the other signs of heat or drought stress. That picture was taken in April 2012. Note there is no sign of dormancy. I'm not sure why that was. Parts of the lawn did go dormant last winter but not the really tall grass.

Bruce, Have you ever used compost recently? you can't expect quick result from soybean meal. It might take 3 weeks for it to work and it won't be dramatic green up like you'd get from synthetic fertilizer. The point of organic lawn program is to improve soil (nutrient cycling), more disease resistant, keep harmful insects under control and it goes on. You just have to be patient. It could take several years to get to the optimal level. Synthetic pre-em can disrupt nutrient cycling by killing protozoa and nematodes. They act like fertilizer spreader by eating bacteria and fungi releasing nitrogen and other nutrients. You might have to spread good quality of compost at the rate of 1 cubic yard per 1000 sqft to re-introduce fungi, nematodes, protozoa and bacteria into the soil to get the ball rolling. Basically light dusting on the lawn and just water them in. All you have to do is apply soybean meal at the rate of 15-20lbs per 1000 sqft every 3 months to keep feeding the microbes in the soil to continue and improve the soil. Soybean meal is fungi meal. It has good amount of protein that will be used to fertilize lawn, trees, etc. Synthetic fertilizer has salts that can ruin microbes in the soil. it's like pouring salt on snail. The spray application I came up with will greatly help for the first few years to improve nutrient cycling. They are food for microbes in the soil. Molasses is basically food for bacteria. Fish hydrolysate and Seaweed liquid are fungi food. I think the biggest problem is that we lack enough fungi in the soil. it is very easy to grow large bacterial population in the soil but not fungi. It just takes time. Over time, you will notice that you will water significantly less frequently because of larger fungi population. They are like sponge with all the holes in the ground. They will be able to absorb more water and hold them longer rather than letting them drain away. I've routinely gone 10-14 days before I've had to water again during the summer if there's no rain. And that's on rocky soil. I can imagine that I'd go 2-3 weeks easily if I had lived on clay based topsoil since they hold more water. A book called 'Teaming with Microbes' by Jeff Lowenfels is a good book to learn about organic practice. It's just not for lawn but how to maintain trees, garden, etc. They have different needs.

Flat blades cut best on high setting. Wind under mower cut best 2 to 3 inch height setting when raise deck above 3 inches air travel changes and blow grass down between blades. Edge of cutting blade get rounded and push grass other than cut blade lap of 2 blade becomes to short. Grass cake under deck cause same problems less cake if use flat blades a lot people like gator blades but cause small grass cutting that cake faster under deck.

Ack I just saw this comment but will try and take a picture tomorrow if it's not completely pouring down rain. The St. Augustine (I think?) in the top picture is the dark green grass under the trees and the clumps in the front yard. The bright green grass I think might be Rye growing over the Bermuda which is dormant right now. Oh and we live in Los Angeles.