Personally, I hate cel bags with adhesive.  The 
first time you bag the cel it's fine (except for 
your waviness problem) but in my experience it's 
very difficult to unstick the adhesive and remove 
the cel without having the stupid sticky flap 
accidentally stick to the cel or even worse the 
background or sketch.  

Now when I get a cel in a stuck-shut bag I open it 
by cutting the flap between the stuck part and the 
opening, so the stuck part stays stuck forever.  
(If that makes any sense.)  The folded flap keeps 
the bag shut even without the adhesive, and if I 
feel a need for greater security while shipping I 
use a piece of the "removeable" type of scotch 
tape.

So, I realize this doesn't answer your specific 
question, but I would recommend just using the kind 
of cel bags without adhesive.  :-)

--Atiya