Ben,
I prefer to double serve, just be sure to use a smaller diameter first, then go over with a thicker diameter. Finding the right combo is the hard part! For example, I'll serve with .014 halo, then serve again with .030 halo. You need to serve the bottom serving tight. Also pay attention while serving the top serving. Sometimes it digs into the bottom serving causing the final diameter size the fluctuate. It takes the right amount of pressure to properly serve the top serving.
Padding works, but I can't get the final diameter of the center serving as consistant, but that's just me. :D