Project size is related with:

CONCEPT: A feasibility study evaluates a proposed system along several independent dimensions: technical feasibility (whether the required technology, tools, hardware/software infrastructure, and technical expertise are available to build and support the system), economic feasibility (whether the projected costs are justified by the expected benefits), organizational feasibility (whether the organization's structure and staff are ready to adopt the system), and testing feasibility (whether the system's functioning can be adequately verified). Each dimension responds to a different characteristic of the proposed project.

APPLICATION: Project size is fundamentally a measure of technical scope and complexity -- more modules, more integration points, more data volume, and more processing requirements. As a project grows in size, the technology stack, hardware/software infrastructure, tools, and technical expertise required to build and support it scale up directly. Assessing whether that scaled-up technology requirement can actually be met is exactly the role of technical feasibility, so project size is most directly tied to technical feasibility.

CROSS-CHECK: Contrast this with the other feasibility dimensions -- economic feasibility centers on whether the project's cost is justified by its expected benefit (a budgetary judgment, not a measure of technical scope); organizational feasibility centers on whether the organization's structure, staff skills, and processes are ready to adopt the system (an organizational-readiness judgment); and testing feasibility centers on whether the system's requirements can be adequately verified with available testing resources (a verifiability judgment). None of these three directly track the technical scale of the project the way technical feasibility does.

Hence, project size is most directly related to technical feasibility.