I got the garden edging with a cylinder on top and an upside down lower case t on the bottom, no particular reason just seemed to be the stiffest. I'll attach a pic of mine
As you can see i originally had the circle on top I have problems keeping the screws into the circular part i need to make a new attachment at some point ( i never have time to do things anymore ) I then cut the rest of it off to make it easier to round on the edges to the original air dam that got ripped off in the middle. It also has a mini splitter on the bottom