Abstract It is well known that cheating occurs in sports. In cup competitions, a common type of sports competition, one method of cheating is in manipulating the seeding to unfairly advantage a particular team. Previous empirical and theoretical studies of seeding manipulation have focused on competitions with unrestricted seeding. However, real cup competitions often place restrictions on seedings to ensure fairness, wide geographic interest, and so on. In this paper, we perform an extensive empirical study of seeding manipulation under comprehensive and realistic sets of restrictions. A generalized random model of competition problems is proposed. This model creates a realistic range of problem instances that are used to identify the sets of seeding restrictions that are hard to manipulate in practice. We end with a discussion of the implications of this work and recommendations for organizing competitions so as to prevent or reduce the opportunities for manipulating the seeding.