A while back I went to Aluminess & had them install a front hitch, a shelf in the Deluxe box & an Expedition Kit:
front hitch
While there Aluminess re-did the support bracket on the Deluxe box that stiffens it for mounting bikes on top. Apparently, the way Sportsmobile did it wasn't the best so they corrected this free of charge. Great customer service there at Aluminess.
They moved the support bracket inside the box
and ran the mounting screws through the swing arm
There are a few holes from where the support bracket was mounted that they plugged up with screws so they don't leak.