Performax 22-44 Drum Sander on Radial Arm Saw

Just bought a Performax 22" Drum Sander that fits on a radial arm saw. It seemed like another toy to get to satisfy my tool fix. Last week I bought the new Dewalt 735 three blade week??
Anyway, I am waiting for the sander to arrive and was wondering if I can buy sandpaper in rolls and trim the paper to fit? It seems much cheaper to buy 50yd rolls instead of the precut Performax paper?
WHat size to get? 6 inch?.

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