For Atomic Duck to be a useful and practical mode of transport, it needs to have space to carry luggage. Obviously, it won't have the same carrying capacity as a bakfiets or cargobike, but it should have enough room for a couple of bags, or some shopping.
While the ingenuity of velomobilists shows the amazing amount of equipment that can fit around a rider, the main luggage area should be able to fit one of the following:
An aircraft carry-on sized case.
Two smaller rucksacks/briefcases/messenger bags.
4-5 bags of shopping.
A crate of beer (as per the Leitra) with a couple of shopping bags.
Using the space behind the seat keeps the the weight of the luggage low. Therefore, as the centre of gravity is moved back, it is also lowered. This means that adding luggage should not affect the rollover stability.
The seat then pivots forwards from its base to allow complete and easy access to the flat-floored area.