Welcome to cel collecting !

Well, when it comes to framing everyone has its 
own opinion. I have been collecting cels for 4 
years and still don't know for sure what has to 
be done.

I believe the plastic sleeve just allows the cel 
not to get dirty, so when you frame a cel the 
sleeve seems no longer necessary to me. I would 
remove it. + the cel could adhere to it with 
time, I have already seen that. The most 
important is the have anti-UV glass.