over time I have found that the paint can stick 
to the inside of mylar bags and cause some 
serious paint loss.  (fortunate for me, I only 
tried this experiment with one cel I didn't care 
too much about)  I still prefer mylar Ds, believe 
it or not.  They are nicer display-wise since 
they are crystal clear.  They also last much 
longer.

I suggest investing in some acid/ligen-free 
tissue paper to back your cels.  I have not had 
paint stick to the tissue  (yet) but if it were 
to happen, the paper would be easy to remove with 
a little water.  I buy my tissue at 
perservesmart.com and then I cut it to fit.

I have the 11x14 size Mylars as it gives you a 
little more room for standard-sized cels.  You 
can fold the bag back and it will stay that way, 
so if it is longer than your cel it is still ok.  
For oversized cels, I just cut a couple of bags 
on one side and overlap them on each corner of 
the cel.

jINx