Just a few thoughts on slings and bipods. First off, bipods are almost as good as a bench rest, assuming they are mounted so that they don't make direct or indirect contact with the barrel. I don't think slings provide the same degree of accuracy, (and yes I do know how to use them), but then again, they are lighter and they also serve as a carry strap and most importantly, you can still use a shooting sling in a kneeling or sitting position, so I think that the shooting sling is a more practical item than the bipod. I find that bipods are great on the range and not so great in the field. When you're out in the woods and you want to shoot something you usually can't get low enough to use the bipod and still see your target.
On an FAL however, they both have a major problem. Instead of being attached to a solid wooden stock, they are attached to the barrel and put tension on it and that's going to mess with your accuracy.