After working with plastics a fair amount, I think that it takes too many pellets to make sheets of plastic. I suggest decreasing the number of pellets per sheet. In my modpack, I've made the following changes:

• in a crafting grid, 4 pellets = 1 sheet
• in a crusher, 3 pellets = 1 sheet
• in a Railcraft rolling machine, 2 pellets = 1 sheet

Added the crafting grid recipe, and created a 3 pellet -> 1 sheet enrichment chamber recipe. If you don't mind, I'd rather not directly add the rolling machine recipe - too much cluttered integration ^^