I used torsion bar in 1983, 1984 and 1985 on the front suspension of the Alfa Romeo GTV6 si Iam familiar with such device and yes we never had any play. We had splines but I believe it is possible to do it with an hexagon or even a square end section but honestly I have of experience of such torsion bar end. However waht I shoud have said is that I have seen sevral of such devices in FS / FSAE with tons of play. I even remember the patch on a patch of 4 screws on the female square section to put pressure on each face of the male square section. So Mea Culpa for the lack of experience on that topic. What I saw was simply a good concept badly executed.

Now, Kevin: ".... the Australian use of the English language is just better" You guys down under are so full of it!