The datum line is molded into the fuse. If you look at the side of the fuse you should see about three small dots that run along the side. they intersect the wing tube, adjuster mount, and wing bolt location. Draw a line through the dots and level to that line. Once you have the model leveled to your thrust line you can set the wing incindence at +3/4 degrees and the stabs at 0 degrees. I hope this helps, I don't trust the canopy rails for the datum line.