I shot some 100 yard and long range groups yesterday experimenting. I can't really say I have anything definitive from testing. It may be that all rifles are different
I shot my light Creedmoor. 100 yard groups varied. I used the tight sling along with a forarm hold with the Stoney Point Rapid Pivot Bipod, and a rear bag. Best was 1/2" and worst was .8"
I then abandoned the sling and just used a tight forearm hold. It shot about the same. I shot a group with this method that was great at 760:
I also shot my "light" .300 Winchester with the 208. I used a tight sling and the forearm hold as with the Creed. Groups were not good. I then shot a group simply off of the bipod while squeezing the rear bag and it went 1/2".
I dialed the 710 yard target and did the same (bipod with left hand on the rear bag) and shot an awesome group. Just made a big black mark that just kept getting blacker...
I guess a guy just needs to experiment to see what works.