How short does your hair need to be for laser hair removal to be effective?

(My Original Blog Post: http://www.latesttrendsguide.com/?p=3121)

I want to get laser hair removal done on my sideburns. They're longer than I like. The top half is made up of thick hairs, but the bottom half is made up of short, thin hairs. Before I get the laser done, do I have to shave off the short, thin hairs? I'm afraid that they will grow back thick and noticable.