Thinner strings are stiffer?
I have always thought that thicker strings would be stiffer and you should string at a lower tension. The following paragraph is from an article from the latest TennisOne website about strings and stringing:
A thinner string is thought to be softer. However, when you string the same model racquet with a thicker string and one with a thinner string at the same “reference” tension, the racquet with the thinner string will have a greater “dynamic stiffness” (firmer feel) than the racquet strung with the thicker string. Therefore, when choosing between similar string but in different gauges, you will want to decrease the “reference” tension of the thinner string to achieve a lower “dynamic stiffness” in the string bed compared to a thicker string. The exact amount to decrease will vary, but consider subtracting 2 to 4 pounds from your normal “reference” tension.