Just a few tips from things I learned when fiddling with sliders.... The high distance you got between the lens and the slider, created the adapter and the rather high ballhead will introduce quite a bit of vibrations. So the lower you get, between lens and slider, the more stable you will be. Best option is a low riding lambda head, and as you level all ready on the tripods you could mount such unit straight onto the sliders mounting screw and by doing so get minimal distance between lens and slider. Also a lambda head can be set in balance also with an even and extremely low resistance which makes pan, tilt while sliding far more easy and smooth then a regular head.
This is 100% correct. I've had issues with top tier sliders (cineped, the slider) down to my personal kessler 3' cine. The tripod head almost always induces vibration and a bit of wag. My favorite approach these days is to put a dovetail on the slider and put the camera directly on the slider with no head, and mount the ENTIRE slider unit on my 7 + 7 Studio or a 2575. Pans and tilts have a bit of a jib feel (which can be nice as the slider can be rotated 90º to accentuate), and it removes most of the wag.