Thanks. Other than address the height difference, the front part provides some rigidity. Without it the chassis (for the most part made of 1" aluminium angle) would be too flexible. I did consider somehow suspending the load below the chassis bed, but since I carry various loads (Pelican cases, suitcases) it wasn't obvious to me how best to do that.

After making the SketchUp plan I made some other diagrams, with accompanying stability calculations (e.g. static tipping criteria, kinematic max cornering speeds etc.) I can probably dig these out.

...and the hitch. I think there are some close-ups in the is thread, or the post your trailer one. Universal joint from a golf cart, couple of large bolts and washers, drilled some holes.