Steve,
I purchased my mod 1 already flying. The builder had also extended the vertical stab and rudder. While flying and operating the rudder I noticed a large deflection of the vert stab. This caused me some concern. After inquiring I was told the mod 4 has a larger stab leading and trailing tube. I added 1/16" flying wires from rudder hinge to top of the bolts for horz stab braces and that removed the identifiable deflection.
Dave