Remember, if the v-tail saddle was cut paralell to the thrust line when you were cutting out the shape of the fuselage, negative incidence will result because of the taper of the fuse. An incidence meter is the best bet to correct any deviations.

Regarding the bubble level in the crotch of the v-tail, I've struggled to identify where it should rest since the v-tail has an airfoil shape. Still haven't solved that one.