Unlike many other phages, the immunity repressor is not located adjacent to the integrase or partitioning genes in the Cluster A phages. Instead, it is far over in the right arm (around genes 68-70 or so).
The immunity repressor's start has been confirmed at the bench, and should use the same start as L5 and Bxb1. There is a large space in the coding genes upstream of the start of the gene, this is because there is a promoter and an operator sequence in the gap. Do not make your immunity repressor too long!