Omigra,
The factory attachment points should work just fine for you. I prefer simple and inexpensive for slings as a rule. But even a bare pair of Uncle Mike's QD 1 1/4" swivels is almost $10 and a surplus GI 'silent sling' to put on them is about $5. Many of the simpler commercial slings don't cost a whole lot more than that, and may well be more secure on their swivels. The GI 'silent slings' occasionally pull out of their buckles if you aren't careful to keep an eye on them.
Slings on pumpguns can be a problem in other ways than 'dumping' the gun if they don't hold. It's important that a sling be attached to the gun in such a way as not to get caught up under the forearm as the pump is cycled forward. That can keep the bolt from closing all the way- not a good thing if you need to get off another quick shot.
The Outdoor Connectiom Express sling (
http://www.outdoorconnection.com/pr...ling&sub_cat=Express+Sling&name=Express+Sling ) is a good simple carrying strap/sling. It's available sewn onto Brute nylon sling swivels for about $20. It comes in several colors and in 1" and 1 1/4" widths. It has 56" of webbing and should adjust out long enough to meet any reasonable need, even on a gun with sling swivel bases a bit further apart than the usual. Despite this, it likely isn't long enough to use as a tactical type sling.
There are several nylon versions of the leather Latigo sling pictured above. Blackhawk makes one, so does Tandy/AA&E Leathercraft, so do a couple of other makers. I have yet to find one of these that is really long enough to use on a shotgun where the sling swivels are further apart than on a normal sporting rifle. Shotguns seems to need longer slings as a rule.
I think QD swivels are the best idea- that way the sling can be removed if it's in the way. But a good sling or carrying strap is a real help sometimes. It should at least be an available option on a serious shotgun.
hth,
lpl