I've been slug gun hunting for 20 years and for the longest time I was against a scope on my shotgun. The majority of my families hunting style for gun season is drive hunting so most of the deer are running and close. I ended up getting a good deal on a remington 11-87 with a cantaliver scope mount so I put a nikon 1.65-5 slughunter on it and I love it. I ended up having a 10-15 yard shot with it at a running doe and had no probelm finding her or hitting her. So with a low power scope I don't think you should have any probelm find the deer for a close shot. Just my two cents. Good Luck!
I'm also looking at getting the Nikon Slughunter put on my rifled 870. No complaints then? I checked it out at the store and at low power I can't see how it could be a problem....Then you have the option of a 'higher' power as well.