I replaced my rear bungee cords with an H-rail. Someone else a while back swapped the front and back units so they have bungees in front and H-rails in the back.
In any case you need to unscrew the whole plastic assembly to remove the H-rail (I did that in reverse on the install). If you don't need the extra width in the tank well swapping the front H-rail with the rear bungee might make sense. You will also have to swap the little cross bungees since their attachments are keyed differently in the front and the back (slide into H-rail vs clip onto the front to back bungee).
Here is a video on installing the rear H-rail upgrade. From that you can see what you would need to do to remove the H-rail from the front.
https://www.youtube.com/watch?v=tpqga1b61OI
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Fish tremble when they hear my name
A ship in harbor is safe -- but that is not what ships are built for.
--John A. Shedd, Salt from My Attic, 1928