I disagree with lineaway on finger height being most important... in my opinion pack thickness is most important. The guy in the video didnt even measure the finger height only thing he cared about is the thickness, if he did care he should have measured before and after sanding the fibers. (so you can decide which you think is most important)
Being a higher level rider, with having much different clutch mods and testing many different clutch pieces in my own gasgas. thickness is all i measure. ive had very good euro friend riders even tell me they dont measure finger height only pack thickness. as it was stated before thickness of the clutch changes the finger height so if thickness is good then height is good and thickness is the easiest to get right so there is no need to measure the fingers in my opinion.
i just dont see how 9.85mm thickness is giving you such a tough pull as it should be killer nice pull at that thickness its not going to be the easiest ever but shouldnt be hard and the clutch at that thickness should work great. Check your master cylinder and make sure the lever isnt tightened so much it makes its harder to pull cause its pinched and also check the fluid in it. (make sure it is not mud looking)
Also i would not in no way just burn my clutch in 4th gear against a wall or tree or whatever but if that works for you go for it. either get different steel or do the sanding method as your going to.
The spec sheet shows a minimum thickness of 9.75mm so sanding some of that off you better watch cause that bit over you have will be gone quick and you will want some extra over that for when the clutch wears... below this the clutch will slip and will not work correctly from my experience. Id say 9.8mm is like the very thinnest id go with it but ehhh i personally wouldnt in my bike cause of wear and cause your stripping off clutch life.