Looking closely at the results from those makes me wonder if there'd be merit to a 'double box' arrangement: On the outer edge (or at a very small offset), have a very shallow box, either straight or angled in, with the conventional 'offset cavity' inside it (blue). The shallow outer box (or 'lip' I guess) might even allow a splitter (red) to be more effective, though my money would be on the inner box cavity.
Goes against the KISS principle of course
but I'm thinking if rounded edges is bad, sharp 90 degree edges is better, maybe sharper-than-90-degree edges may be better still? Unfortunately I'm not in possession of a large truck fitted with precision instrumentation to try it out
