Final answer:
The authorization of spandex shorts with IPFU for soldiers must be checked in the latest Army Regulation 670-1, which governs wear and appearance of Army uniforms.
Step-by-step explanation:
The question at hand pertains to the authorization for soldiers to wear commercially purchased spandex shorts with the Improved Physical Fitness Uniform (IPFU). Although the background information provided discusses historical aspects of military uniform regulations and behavior monitoring, especially during times of leave, it does not directly address the current regulation for the wear of spandex shorts with the IPFU.
It's important to refer to the most recent version of the Army Regulation (AR) 670-1, which details all approved wear and appearance of Army uniforms and insignia. The specific guidelines about spandex shorts would be included there, and typically such guidelines are detailed to maintain a professional appearance and functionality during physical activities.