I know this thread is old, but I thought I'd post an update:
I ended up cutting the pads into approximately 4 inch x 8 inch rectangles. I started using a pair of scissors, but that got old fast. I ended up using one of those razo blade knives (you know the ones where the blades are scored for you to break off the tip when it gets dull?). Used a piece of 2" x 4" for a straight edge. Dangerous - I know - but I wore kevlar gloves and was very careful.
Anyway, that worked well.
Bottom line: big pieces worked fine. I put the cut up pads in mesh laundry bags and arranged them in the barrel filters. Got rid of the UV filter and had clear water all season. I hope that continues this year. I'll be starting up the filters again in the next couple of weeks: Spring starts early in New Mexico.