Advise on inside length

I've noticed in some of the pictures posted here that their sleeves fit perfectly against their pubic area making for a nearly seamless transition.

This is exactly the look I want!

Were going to start with a Barney and I measure 4" long. So should I order an inside length of 4½ to get that perfect fit at the base of my penis?

Any advice you guys can give me will be greatly appreciated