Mine are flexible at the bottom as well... I scrape them regularly leaving my driveway if I go too slow in my normal "Low" ride height.
That is something to consider for sure with the Rally Armor ones which are ridged, just not sure how low they hang overall. They cover much more in the upper fender though which is the ideal coverage when running fat wheels and/or spacers.
EDIT: just noticed your link is actually the same as mine... BEEGROW brand.