Looking at the common airframe used in both the underfoot quad posted July 9th of this year and the overhead quad posted two days ago on July 16th, the reason that the latter has the more compact footprint is clear from the diagram above. It includes 32" propellers and a 12" centre-section, just large enough to fit the mannekin's seat.
There's not much space there for dangling your feet, unless you want them sliced like salami. Put the quadcopter overhead and the problem is solved, however. Remarkably the weight of each airframe (the single-decker and the cubic or double-decker) turns out to be the same at 8.40 kilos, but then the former has a 42" square footprint and the latter only 25".
Nonetheless I still figure that upping the footprint of the cubic 'copter to 34" square and using the preferred 1/16th gauge alloy section that I can still bring the airframe in at around 15 kilos, which allows for two battery packs and the motors and ESCs and is still under the regulation 25kg for a regular drone... but without the seat and dummy.
There would though be an argument for getting it flying sans payload, and afterward registering to as a large remote-control model (of which some in the UK exceed 100 kilos under the same scheme). The great benefit of the design however is modularity, in that the drone used in the single-decker version is the self-same that can be fitted up top.
In practical terms this means that the quadcopter can be flight-tested independently and afterward supplemented by either the seat and dummy (albeit with the restricted leg-room), or else raised into the overhead within the outline of the double-decker. At the end of the day therefore it would be for prospective operators to decide whether those propellers are preferred overhead at the cost of the extra weight.
Certainly from the point of view of safety that is the better place for them to be, while at the same time providing for a more compact footprint altogether. What is intriguing about the outline pictured here though is that it would still accommodate a passenger stood within a booth instead of seated, which again is a matter of personal preference. (It also begs the question as to where to fit avionics, though apparently flight-control computers can be operated inverted, so that they might be fixed beneath the base).
It's a dilemma with designing electrical air vehicles though: with helicopters there was certainty from the outset, with their main-rotors above and tail-rotors at the rear.
Now though we are cast into confusion, and Mourning Becomes Electra.