CTBs come in different sizes and are divided into two types. Regular packages and scientific packages. Packages are arranged in the gateway module, which is not difficult to do. I chose a circular layout and I have 318 CTBs (equivalent to 6156.8 kg) and a 1.2m x 1.6m crew path, enough to meet the requirement of 160 CTBs and 0.8m x 1.1m Crew Translation path dimensions.