I have a hollow 2024-T3 rectangular bar and need to check its mechanical and physical properties. So i went through the MIL-HDBK-5J, and it have 3 choice for this material; 1. Sheet 2.Drawn tubing 3.Extruded Bar,rod,and shapes. so for hollow rectangular bar, which one should i choose. 2 or 3? and if I have solid rectangular bar, it will be the no 3 right?