While sailing upwind stand where you can sight up the mast and watch how it changes shape when going from min to max settings. Do the same at the headstay. You'll get the idea.
Backstay tension does affect headstay tension on a fractional rig boat, but not to the degree it does on a masthead boat. The amount of effect depends on the spreader configuration and other elements of your rig. See it for yourself.
Last edited by SteveInMD; 06-12-2009 at 08:24 AM.