Rondar published a 2009 Tuning Guide for the Viper 640.  The document includes a discussion of the Viper 640's critical rig controls,  fundamentals of setting up the Viper 640 rig for best performance, and quick reference tables for both rig tune and sail trim settings appropriate to different wind strengths.  Those rig tune and sail trim tables are suitable for lamination to carry with you on your boat as a quick reference tool.

We encourage all Viper sailors to download and read this guide, and put its recommendations into practice when setting up your boat.