I cut mine at 3.5" currently on my X590 54" with mulch blades/kit installed and for the most part I'm happy with the results. Any higher than that then the lift of the blades are almost nonexistent which can miss more grass. I do notice that because of the mulch blades not lifting quite as high I sometimes will not let the front left wheel go over the grass I'm trying to cut. This obviously is not making most of my deck width but I'm happy with the compromise. I have considered in summer time when is grass is thinner to just switch to the high lift blades with mulch door open when I go above 3.5". I shouldn't have too much grass clippings at higher cut heights and when I get close to a landscaping bed I can just close the door.