Flaming River 1505M manual coupler kit - sloppy?

I have no real complaints over the OEM coupler but I have a Flaming River power to manual kit with double D shaft and u-joint. I have this question into their tech dept but looking for user feedback here.

Manual box has clean, sharp splines with no signs of wear. The OEM coupler fits over it snugly with no slop whatsoever. The FR universal joint slips over the box splines very easily (almost too easily) with some rotational play.

Step #15 of their install sheet says to install a shoulder bolt, followed by the set screw. The set screw is supposed to "remove end play from the steering coupler." There is no shoulder bolt or hole in u-joint to use one - only the single set screw.

I cannot see how this set screw, even torqued to their specs, is going to prevent the slop in the spines for more than about 5 min. Your experience?