Newcastle, yes, the target configuration is the more stable of the three, there is another single point setup that cuts down any twist, it uses the bren sling and wraps around the forewood/topwood, with a twist to stop any load on the swivel, much the same setup we used with the SLR in competition, but as it is against the rules of service rifle shooting, I did not bother to show it.

Thunderbox, we also use the lockup sling in single point, however, as some matches are commenced without the sling in position, the sliding loop makes it quicker to get your arm in, tightening is automatic and can be painfull, but as these are rapids, they don't take long.

You will notice that there are 3 standard slings and a Owen sling(short), the Bren(long) sling can and is also used, but excess material becomes a hinderance when rapidity of movement is crucial, we often use the long sling for deliberate shooting.
The belts all are setup with a half twist, to ensure they lay along the wrist and don't cut in, there's only so much pain you can handle at once.