7 tail on a 6
I have done the 7 tail on a 6. The considerations are, if the new 7 tail had been previously installed on another airplane,the attach bolts may not align exactly with the existing 6 holes, the FG empenage fairing will need some modification. Of more concern is the W&B the 7 tail is heavier and the rudder has a heavy counter weight, this with a long arm will affect the W&B. Other than this it will work fine. Van's may have other concerns, but I have done it and the airplane fly's great.
Dick