[Roger]

After two weekends using them on my fields (WPI and UMass Dartmouth) I can say the plastic flaps held up nicely with no rips and only minor scars along the top. Very few zipties popped. Every few matches in my rounds I'd adjust them back to spec -- "evenly spaced" which ends up around a one inch gap between them. There are two holes for two zip ties either side to keep them on, and a ziptie each flap side around the bar to keep them from sliding too much.

There have been a couple of boulders that managed to roll up to the flap and push the flap a little under the bar, but none (that I saw; I can't be everywhere ya know!) ever got thru. If your robot drives thru fast enough one or more flaps swing up and over, or just roll up, which I guess is where the scars on the top come from.