  Wilson et al. propose a measure of flexibility in project scheduling problems
and propose several ways of distributing flexibility over tasks without
overrunning the deadline. These schedules prove quite robust: delays of some
tasks do not necessarily lead to delays of subsequent tasks. The number of
tasks that finish late depends, among others, on the way of distributing
flexibility.
  In this paper I study the different flexibility distributions proposed by
Wilson et al. and the differences in number of violations (tasks that finish
too late). I show one factor in the instances that causes differences in the
number of violations, as well as two properties of the flexibility distribution
that cause them to behave differently. Based on these findings, I propose three
new flexibility distributions. Depending on the nature of the delays, these new
flexibility distributions perform as good as or better than the distributions
by Wilson et al.
