I agree, but I'm also not certain. Another option would be to let him slide through a damp washcloth a few times. This'll often help loosen stuck shed if it isn't too extensive. His might be too bad for this, but it's worth a shot.
Also, RIs can be aggrevated by too LOW humidity too. So I really don't think a soak would hurt. Do you have a good herp vet? An exam to see if he's truly over the RI might be a good idea. And a vet can give you the best advice in this area... Good luck with him!