[tqtran]

I shorten my single point sling and wear it wround my neck so that the stock rests on my chest.

 

[tqtran]

IMO the most comfortable and easy to operate single point sling is the Stargate sling from TheVestGuy. Simple snap removes the gun from the sling and it evenly distributes the gun's weight around your shoulders.

 

[tqtran]

Although, for a right-handed shooter, wouldn't you want the buckle on the buttstock of the PS90 to be on the left side of the rifle?

I do have it on the left side. I just put it at the very end of the stock in this picture to show how it connects.

 

[tqtran]

I'd like to see a pic of how the sling system distorts when the rifle is held to the shoulder (in firing position), if at all possible.

Ah...me taking pictures of myself holding guns will result in my wife laughing at me for years to come.....I'll have to take a pass

Is there any discomfort (pinching, rubbing, etc...) when firing the rifle with the sling attached?

No discomfort what so ever. You don't even notice its there. I always shot with the sling attached. I don't see the point of taking the gun off a sling unless I am switching guns.