Attended a CMP clinic and learned a lot.  So far have been to 3 shoots (all course A) so far and looking to improve myself.  I am currently using a 20" upper standard barrel with A2 stock and 4x optics and 2 stage 4.5 pd trigger.   My question is how do I know if I have my sling is too tight or loose?   I tired prone with different sling tightness and they seem all the same to me.  I have read not to adjust it too tight due to the sling pulling the barrel.  I cannot use a free floating barrel as it is not allowed in a as issue class.  I have notice that when I sight my rifle from a seated position with a sand bag rest, my poi are are different when I shoot prone slinged up; is this due to the sling being  too tight?  Unfortunately my range only allows shooting from a seated bench position so I cannot try different positions nor use a sling.

Another question I had.... if I use the current sling length for my prone shooting, during off hand... won't my poi be different due to no pulling pressure on the barrel?  Should I just leaving my sling position the way it is for prone and adjust poi for offhand.  I figure that shooting off hand should be the same as shooting from a bench due to no sling tension so my zero from the bench should be good for off hand?  Read a lot of different answers online but not really a clear answer.  Thanks for any advice and feel free to ask me as many questions.   I wanna learn as much as I can. Thanks everyone

It takes practice to develop the "feel", but consistency is key. The position should be built the same way every time. Each part should have a reference to another part. My support hand is against the sling swivel and support elbow under the left-rear edge of the magazine, so any change in sling tension is felt in the shoulder and seen in the Natural Point of Aim.

If you're shooting at one distance (200yds?), record your zeroes for each position. If my carbine was put back in as-issued, I know my Sitting and Prone zero is up 1.5 MOA and left 1.5 MOA from Offhand.

My local match is 100yds. With an NM, my Offhand is 1 MOA higher than Sitting and Prone because of less support against the trigger pull. Other than that, my zero is at the mercy of light (irons).

Bench construction varies, but I've found that my "bench prone" sling setting is about 2" too tight for real prone.

Ok, my shoots are done at 200yrds during the entire shoot so my scope is adjusted to that.  Honesty my prone is descent but my offhand is horrible.  Seems very unnatural and the swaying kills me but learning and dry firing to become better.  I just wanna make sure my scope adjustments is correct when standing and during prone due to sling tension on prone.  I've seen some guys adjust their sights during prone/rapid prone/ and standing while others set their sights during sighting and leave it the same throughout the course. I do appreciate the advice and info.

Off hand is the hardest for anyone..  and with a scope it makes it even harder due to the magnification.. movement seems amplified with a scope.. Iron sights are easier to shoot in off hand in my option. Im sure some will disagree.    The main thing for me is my breathing in off hand you need to get into a routine with each shot. you will have to develop it on your own..

Why wouldn't a NM float tube be legal? Or a quad rail

They are legal for all CMP competition

Not Modern Military, technically. There's still no base as to what "accurizing" is, which causes some fuss.