I am done with having my sling wrapped around the foregrip and buttstock and have decided to get side swivels.  I have looked at the GG&G products but was wondering what else is available or recommended.  Are there any problems associated with mounting the swivel the the front sight tower?  (i.e. torquing the tower out of alignment while running with the rifle.)  Also, I am thinking of buying a rail system.  Would I then want to mount the front swivel to the rails?  If so who makes a swivel that mounts to rails?

In theory, anything tugging on a barrel could affect the point of impact; nonetheless, unless you're shooting X rings, I doubt you will notice the difference.  

Knight Armament makes a rail mountable sling attachment that is similar to GGG's design.   And if you attach it to rail system other than a free float tube, the net effect is the same as mounting it to a sight tower.