BTSThe amount of backlash in the radial bearings when the tail is stationary is not of huge relevance as there is very considerable force carried by the thrust races when the tail is turning.
The way that the loads are carried in operation, the thrust load is transferred from the hub through the thrust races which bear only
on the outside
races of the radial bearings. These outside races carry the thrust caused by the centrifugal force of the spinning grip. The backlash you feel is the acceptable tolerance of the radial bearings. The bearings are designed to support a radial load, not a torque or twisting of inside race versus outside race. This twisting of the races is what you describe as slop. The backlash is not present when the tail is turning at full speed. Even if you pull lightly on the grip, you will see that it is quite stable... just imagine how much force is on this bearing stack at 8,800rpm or so on your Raptor 90.
I have two of the QUK tails and they both work superbly, setup easily on the gyro and I have the peace of mind that they will not throw a grip/blade.
We the cosumer has a choice however. I am happy with my QUK and I have no doubt you're happy with the Kasama.