Quite a few years ago we bought a First Up screen room, same thing as an E-Z Up, and it sure didn't sag from trapped water nor did it need any "grommeted holes" as we
never had any issues at all with rainwater draining off.
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It's greatest downside - it was just 10' x 10' whereas this new Coleman I just purchased is a much more useful 13' x 13'. For our use we also found the screen sidewalls to be a PITA and eventually didn't bother with them. When we camp in early spring / late fall with friends with their own shelter we've found that hanging a tarp or two across a couple of the sides helps enormously to block the wind. IMO a shelter is a great campsite accessory if you're willing to put it up & take it down. :D