If the vertical fin is "twisted" or rotated in relation to the fuselage centerline it will cause the plane to yaw slightly. If the vertical fin is offset slightly from being on the centerline of the fuselage the effect would not be very noticeable but should still be avoided. If the vertical fin is mounted properly but leans slightly it will induce a slight amount of pitch when the rudder is moved (like V-tails).

Full scale single engine A/C actually have their vertical fins "twisted" or "rotated" slightly to compensate for engine rotation. German built ME-109 A/C had their Verticals offset in one direction but Spanish built ME-109's were offset the opposite way because their engines rotated in the opposite direction. The ME-109 in Harlingen,Tx was Spanish with a German motor retrofit. VERY hard to fly I heard for this reason.