I just installed these on an Arrow X1 and they are great. It’s your choice as to whether you install on the top only or both top & bottom. Most are only on the top. Things to know, the hole in the chassis yoke has to be 22mm, I had to buy a reamer and open them up, at least on my 10mm kingpin ones. You have to drill & tap 2 M4 holes for each adjuster base to bolt it to the frame. And my kingpins were too short with the Sniper units installed and I had to buy shoulder bolts and drill them for a cotter pin.
After all that though I love them, very quick and easy to adjust. With my Sniper lasers I set the toe and camber in about 5 minutes from scratch.