Some people say that instead of using tape to 
hold a cel in place, they use photo corners? I'm 
not sure how this would work unless they did 
photo corners on the bottom too, but one of the 
reasons you only tape on the top edge is so that 
gravity can let the cel hang naturally. But photo 
corners would avoid having to deal with tape at 
all and some tape can be very strong. If you put 
strong tape over a painted area on the back of a 
cel, I don't want to even think about the results 
if you try to lift up the tape. *cringes*

Just another thing to consider.