Slider-tripod flexing- How much is okay- How to test fix

Sliders get flexing during shooting when mounted on tripods? Take a look of this video shared by Simantov, it shows you the testing way, normal scale and fixing way of the flex and how important it is to select a suitable support for sliders. From the video we can see that only one tripod is needful to support iFootage Shark Slider S1 Standard stably with less flexing. iFootage Wild Bull Tripod T5/T7, one of the ideal choices, can achieve it.