I just came across your talks and I hope you don't mind I jump in. I saw the video of the jumping around you are having. I see the flex forks working as well as they can to keep up with the washboard type lawn. Yes the machine goes in excess of 15MPH but that is just for transport only. It is meant to go from point "A" to point "B" at 15MPH to cut down on transporting it to each job, not mow at that speed. With the limitations on blade tip speed no mower can mow that fast. What is your rear tire pressure at? 14lbs will really get you a hard ride. You can go down as low as 8lbs but me mindful of slopes and curbs. The flex forks are shown at dealers with the same thought of car dealers. When you go test drive a new car is it the stripped down version or does it have the options available being shown. I also noticed your arms are not on the armrests. Lower your hands down on the steering arms and that will allow you to use the arm rest, this will help with the jerking forward and backward. Think of the deck springs as a counter weight for the deck. The closer you bring the two set nuts together the lighter the deck becomes, the further you spread them the heavier it becomes. Any chance of seeing a side by side with another mower video?