...for me, I cut cel-bags in two and place them 
between the layers, then placing them all in one 
bag, and this way I use less bags and use them 
more efficiently. I would definitely bag them, as 
sometimes sliding has led to minute scratching on 
the surface. Plus, they can and do stick to that 
paper...and, as Trebby once said, "I don't trust 
anything that's dyed black is 'acid free'."

-Misha