I had to do this a while ago when I put the wide kinetic pad on to the vespa trans. I was never getting full rear brake engagement, even though it felt like it on the lever, and this was why. I am running a vespa trans in a Kinetic hub/wheel, so it might not be as much of an issue on most setups, but some may still find it helpful, especially with worn brake pad or lever components.
First, the different brake pads available, kinetic, vespa wide, vespa skinny:
I noticed the vespa lever bottomed out before i got full pad engagement in the drum (a little hard to see with the sharpie already marking where i'm going to shave it).
I compared the levers, the Kinetic lever is clearanced there, and the 'finger' was not as worn, so it got me awesome engagement, but it is shorter so provides less leverage.