A different brand prop may require a different pitch setting. Even a same brand prop of different diameter will. So I would set it up for a recommended static RPM for that prop and then insure you are getting 6800 rpm on takeoff roll. What was your static RPM with the GSC propeller? I have read anywhere from 6100-6300 rpm for static, but I am an new Kitfox owner so will defer actual numbers to either more experienced owners, or to the prop manufacturer. I'm sure if you called Warp Drive and told them your which of their props you have and that it is on a Kitfox they can tell you what static RPM you should set.