Jeff,
When cutting slips, use a new blade, score the back side first, flip it over and place it on a sanding block (for support) then start from the middle and cut to the edge, rotate 180 degrees and cut the other side.
Go here for more notes: http://www.uilleann.com/reeds.html
Evertjan 't Hart has two (essentially the same) reedmaking websites: http://home.wxs.nl/~HartDD/Reed/reed.html http://home.planet.nl/~HartDD/Reed/Intro.html
He cuts through the bark with the edge of a small file.