Having the loads applied on the lower fiber will result in more shear reinforcement compared to when the load is applied on the upper fiber.
This is because when loads are applied on the upper fiber, Eurocode allows to calculate the shear reinforcement with a reduced shear force ( it assumes that close to the supports, are directly transferred to that support). The reduction is calculated according to EN 1992-1-1 §6.2.1 (8) (for distributed loads) and §6.2.2 (6) (for points loads).
When the load is applied on the lower fiber, the reduction is not applied.
Remark
Diamonds supposes at all times that the loading is applied on the lower fiber (most conservative).
