in the enclosed picture are three examples of types I'm speaking of. In the top picture, the lift struts are attached via a single eye bolt. The eye bolt is obviously vertical through the wingspar
I looked at the rudimentary engineering drawing elsewhere on this site showing the forces acting on the wing spar, and get that the wingspar is tending to make an S curve. Let's assume that the wing spar in question has an internal sleeve doubler to effectively increase wall thickness to resist compression and prevent the collapse of the tube.
In the middle drawing, the most common method method. Two straps fore and aft, attached via a bolt horizontally though the spar. I have an elementary understanding that this second, commonplace method puts drilled holes through what I believe is the "neutral axis" of the spar.
finally, the bottom illustration of the "texas parasol" type of fitting. It shares a commonality with the eye bolt in that there are holes drilled through the compression and tension axis vertically through the spar and attaching a u shaped bracket to the bottom of the spar into which the lift strut is through bolted. Two holes, albeit smaller in diameter than the single but larger hole of the eye bolt.