You could do some "rod inside tube" modifications. Cut off the 30 degree bends with 4 cuts and find rod that fits the inside diameter and insert two sections as internal sleeves and reattach rear of OEM rack now flat. Secure with through pinning, bolts, brazing, epoxy, whatever works if you can't weld. You could even bend up an entire replacement "U" to extend rack rearwards.
Your subframe at the rear is capped by simple plastic plugs. I removed mine and inserted a "U" shape of vice bent 7/16ths (?) solid rod creating a rather strong extension used as both a grab bar and base for picking up the cantilevered load from my original homemade rack. Worked great. Once I got a Cyclerack I tied cycle rack's Rotopak mount to this same homemade grab bar for much improved no-cantelever rigidity.