I've been using a digital level on my build, and have noticed a problem. I'm not sure if it's a precision issue with the level or a serious problem. The Hummelbird has a 72 inch wide center section of the wing that goes through the fuselage, front spar is built up, rear spar is a 1.5x1.5x.125" aluminum angle. Front and rear spars were installed and both leveled to 0.0 degrees, identical distances from each other at the ends. I installed the ribs, made the skins, measured at various random points along the way to confirm level. After I riveted the skins on, the front spar was still at 0.0 degrees, but the rear spar was at 0.5 degrees left to right. I have no idea how or when this got skewed. What would the tolerance on this be? I've tried replacing the spar with another piece of angle and shimming the center attachment, but that made little difference, 1/8 thick shim on one side (way more than I'd feel safe using) resulted in a 0.1 degree improvement. So it looks like I'll have to take off the bottom skin. I have a 0.00000001% chance of drilling that many rivets out without enlarging a hole in the ribs, replacing a rib means I have to take off the leading edge skins as the ribs are riveted together through the front spar. Basically, I'd be undoing the last 6 months of my build, the most unenjoyable slog I've had in the whole process, and re-doing it. I'm not sure I have it in me to do so, if this is really necessary, it may be the death of the project. Any suggestions on how to fix this? Is this something I could live with and fix with aileron trim, or a going-to-kill me type problem? What would be the effects of this? With an 18' total wingspan, could I fix it with the outer wings? I'm not going after perfection with this project, just good, so it won't bother me if it's imperfect as long as it's safe. Edit: Outer wing panels are inclined by 3 degrees, I believe, relative to the center section wing stubs.