Well, that's pretty slick. You just need one for the engine, made out of that same aluminum angle you have sitting in that one pic. Attach it to the engine where the prop mounts, add the level or have it glued to it. If the bubble goes from line to line, and you manage to match the two, I would say your incidence is zero compared to the thrust line. You can just set a level on the horizontal tail. Mark the levels with some sort of fin line graduations every 1/16" just for refeence. With experience, you will be able to split the hairs pretty good and hit those 1 and 2 degree settings.
Thanks for posting,
Dan McEntee