Getting the stabilizer hinge line parallel with the wing hinge line is critical. Get it off and the plane will never get trimmed. As bad a a permanent incidence problem.
I got tired of using yard sticks, measuring tapes, punching holes in the covering, etc. I don't remember how or when I came up with this idea, but I have never seen it published and no one showed me this. Just lucky I guess on coming up with it out of frustration.
Take two 1/8 or 3/32" square strips of spruce and lay them over the side view of the plans. Drill two very tiny holes at each end and ACC in a large Tee pin in each end.
Attach the stab and pin /glue it in place, but loose enough for moving it slightly. Take one of the spruce spars and place the pin in the TE/LE gap of the Stab and then the wing. Do the same on the other side. Then make sure, using a 90 degree triangle, the two spars are square to the TE/LE of the stab. This will make a true rectangle and the stab will be true to the wings TE, this works even if the TE is swept forward because the spars are placed at the same place on each side. I use Ambroid to give me more working time and if a mistake is made, I can use Acetone to loosen the stab and redo it. By doing this with the plane upside down, the incidence will usually also be zero. That is if the incidence is supposed to be zero and assuming the top of the fuselage is in line with the thrust line and wing center or chord line.