Just uncovered my stacks after my first winter covering the wood. Used 'heavy duty' tarps. Used bungee cords through grommets, then hooked to nails in pallets. Tarps held up fine - one small hole (which will become larger....). I made sure to take some old rags and placed them under the tarp where corners and other 'sharp' spots were obvious. But......the tarps weren't cheap, and if it turns out that I only get 2-3 years out of them (I'm covering ~ 15 cord), I'll have to try something else - too expensive (probably dropped over $100 on tarps - so, not replacing the tarps often) to replace often. For next year, I was thinking about taking some ~ 8mil, cheap plastic and cutting to pallet dimensions, then stapling a folded end to the top layer of wood, then tossing a some punky wood on the corners to keep wind rippling low. As long as it keeps the leaves, snow, ice, etc. off for the late fall and winter, I'll be happy - I leave my stacks open for the spring, summer, and most of fall. Yes, I know, the plastic will probably not work......
Cheers!