I followed the advice from the Matronics forum, and used a small flat file to debur the stringers. In addition, I purchase a countersink/deburring bit from Avery that fit my Sears electric screwdriver. It turns very slowly and worked great to debur the inside of the horizontal stab skin. I also began to remove the plastic from the outside of the horizontal stab skin. Difficult, but much easier than the inside of the skin.
