using a 5/8" is sort of between SC and IM. I know there are some studies floating around on this forum which shows that the SC absorption is as sufficient, equal to IM. Also, men's thighs tend to be leaner therefore less tissue to pass through anyhow.
Dr Crisler had posted some good stuff on SC injections and its efficacy. I personally notice zero difference in my routine labs between 1" IM in the glute versus 5/8" in the thigh.