Practical experience suggests that the use and understanding of UML diagrams is greatly affected by the quality of their layout. In previous work, we have presented evidence supporting this intuition. This contrasts with earlier experiments that yielded weak or inconclusive evidence only. In the current paper, we expand on our earlier experiments by varying both diagram types and populations studied. We find no difference in the beneficial evidence of good layout wrt. diagram types. We also find support for the hypothesis that experts benefit less than novices. While still lacking independent replication of our earlier results, these results add further evidence in support of our hypothesis.