At what point on the recoil scale should one consider mounting the sling stud on the barrel? Does mounting the barrel band have any serious effect on accuracy while shooting from a sitting position with a tight sling (barrel measuring approximately .700 at the muzzle)?

I have concluded that they are not really needed unless one doesn't properly hold on to and "roll" with the rifle when firing it.

My forward hand does not move on the fore end when I shoot, even with my .500.

Still, a barrel-band mounted swivel looks cool on a rifle.

And with the swivel so far forward, when such a rifle is slung it stays low behind the shoulder, which is handy for carrying.

Tightening the sling on such a rifle will change POI as much as a few inches or more at 100 yards, depending on barrel profile.

I have done that even with very heavy and stiff barreled rifles when experimenting at the bench.

Hello,
Match built 15/16 rifles will have a float tube under the handguards to avoid pressure on the heavy/stiff/short barrel they use, otherwise the POI will change due to the sling pressure you mention(sitting or prone.) Would not be a problem if you could exert the same pressure for each shot, but that is not going to happen. Not really a serious problem with sporting rifles of heavy recoil for rarely would one be taking extended range shots, as in 300 plus yards, with such a rifle and would think the variance at 100 yards would be minimum. Recoil from 470NE and 458Lott does not shove my hand into the swivel/stud so probably is more of a cool factor than anything else.