..for optimum cut. I have my Lazer at around 3800 no load.. I've noticed less stringers by cutting back on the rpms to around 3500 under load (vs 3600+). Is it possible the lift is too great, and its blowing the grass down under the blades? I'm running excalibers notched foils. The deck has the anti blow-out baffle, OCDC, and striping roller, and cuts 1/2" lower than the indicator shows...I usually mow at 2.5" to 2.75" (actual height from floor by blade tool) any higher, and too many stringers!