Yes indeed Charlotte ... for stability in any position, a sling should be considered the #1 accessory for any competition shooter ... and yes I said ANY position, even Offhand ! I have been having an ongoing feud with Gary, the head of CMP, for years in that they totally mss the boat in denying the use of one in the Offhand position in Sporter Rifle competition ... and more to the point in even allowing single-ended slings in a Sporter/Hunting Rifle event !
But enough of my soapbox rantings ! Typical formal rifle competitors mostly use a single-ended sling arrangement ... the sling is hooked to the forward swivel and runs straight back to the upper arm left arm, (for right-handed shooters), where itis looped around above the biceps/tricep muscle mass. It should be tight, but not so much that blood circulation is impeded else a definite heavy pulse beat will be transmitted to the forearm of the rifle. In essence it locks the upper body/arms/elbows into a rigid "tripod-like" position. For those who use the sling in the traditional manner ... as a rifle carrying device ... the sling can be adjusted in length such that by inserting the left elbow into the dangling sling, and then allowing the forward section of the sling to pass over the forearm near the wrist, a similar degree of support can be achieved. This arrangement can be used in any position.
Mick