I have never used a footprint and have never had problems! IMHO, footprints are greatly overrated and are mainly a money-making scam for the tent companies and outdoor stores.

If you're not convinced that a footprint is unnecessary, a polycro sheet will last a season or more. It's plenty durable enough. After all, polycro storm windows are designed to last through a stormy winter.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey