Are you planning on keeping it? If so, it doesn't 
matter as long as YOU enjoy it. Many collectors 
make all sorts of modifications to their cels: 
filling in missing paint, correcting line 
fading...the list goes on. I however would not 
cut the cel if it means cutting away the sequence 
number, AIC stamp or any other indication that it 
is a true cel and not just a good piece of 
fanart. Just remember, trimming the cel hurts the 
value.