If there's a minimum and maximum pressure indicated on the tire its related to the tire construction. Picking the 'right' tire is a combination of identifying the characteristics you want from a tire and picking a tire specifically engineered to deliver that.

Personally if you want to roll at a lower pressure I'd suggest you shop for other tires. 26x3" Kenda Flames used to be rated for MAX 40PSI. Nokian 240's used to have a single INFLATE TO 65PSI rating on them. Doing anything else just shortened life expectancy and compromised performance.