I’ve used this option on WACO Mosquitoes and a Mirage. I highly recommend it.

When you are setting up a V-Tail plane for squareness, try this;

With wings attached and tail assembly slipped on fuselage, turn the plane up side down on a flat surface with both wing tips touching the surface. Now just twist the V-Tail assembly around until it too touches the surface with both halves of the tail.

Voila! Instant alignment.

The trick to keeping the V-Tail assembly from accidentally twisting around during flight is to add a tiny drop of CA glue to the joint then tape around the fuselage with electrical tape.

The drop of CA will keep the tail assembly in place, but it won’t be enough to keep you from breaking it loose to remove the tail whenever you want. Good Luck!