A couple of things about levels.  If you're using a bubble level you must test the levels in the store because after a report from my cousin who is a highway engineer most of the levels are not accurate.  You test the level by setting the level on a flat, apparently level, surface.  Look at what the level reads.  Now turn the level 180 degrees, now what does the level read.   A good level will show the same amount of inclination.

We set the wings up using a bubble level which read correctly in the previous test.  Next we used a smart level and made the same test.  We were two degrees off.  I know it cost more to buy a smart level, but it will save you big headaches later on.