There is an easier way to do that.

First mount the wing, following the instructions.

Then dry install the stabilizer, making sure that the stab is centered from side to side and is parallel to the wing, looking from the back.

Measure from the trailing edge of the wing straight back to the trailing edge of the stabilizer (not the elevator) at the tips and be sure they measure the same on both sides.

Draw lines along both sides of the fuselage on the top of the stabilizer as a guide.

Now glue the stab in place and check both alignments (from the rear and from the top) frequently until the glue sets up.

Jim