MY FW is 21'. The manufacturer asks for bed and bed rail heights so they can adjust the axle to fit your truck during manufacture. They fit on what I'll call mid size, like the Frontiers, up to F350 4x4's. On the F350 the top of the tires were even with the bottom of the trailer body, looked a bit off but it works for the owner.
The original Escape single axle FW was designed for small and midsize trucks. They just came out with a new twin axle model mainly to make it compatible with today's taller full sized trucks. The new one has 3 height positions, springs under the axle, over the axle, and has hangers that allow the springs to be dropped a couple inches. The pin box height can adjust some, as well as some of the hitches.
Happy Motoring
Bob & Deb
W Ma.
12 F150 HD SCAB EcoBoost LB 4x4
14 Escape 5.0 TA