Hi Conrod,
I use the incidence meter on the wing I then level up the back of the fuse so its level & the wing is at zero degrees I then put a little hand held level running down between the two tail Vs I also recheck it by putting a ply 1/8 Plate between the two v- tails & put my little level on top & it reads that the bubble is still in the middle like the wing so this now tells me the tail & wing are at zero degrees. I also use a big square hard against the fire wall & there is no gaps between the level so this tells me the fire wall is level. I appreciate your return comments to see if this is right, or how you would do it.