Gonna put a Sling on my 20" 590.

Probably going to go with standard two point for field carry on these. My question is does anyone have any sling experience with these? They are a little longer than the 18.5", do they knock around too much? Should I opt for a 1" or 1 1/4" sling? It is the 20" Mariner with a heatshield, Speedfeed stock and will eventually wear a sidesaddle so it is not a light shotgun. I don't want to keep buying slings so I want a good sturdy one. I've run a 1" web sling on an 870 before and I trusted it, but this a much burlier gun...

any recommendations for a two point sling? any experiences using one with the longer 20" 590?