Sure thing. Below is a picture of the right outer wing panel. I made the joint right at the engine nacelle. (see other pictures). The square carbon fiber tube is 3/8" (10mm). You can see the foam box spar. The stock plane uses nesting foam box spars. I did not use this. I kept the single larger foam box spar design through the whole wing. It's hard to make out in the picture, but inside the foam spar and surrounding the carbon fiber tube is a 3D printed block, about an inch deep that is a spacer to fill the space between the carbon fiber spar and the foam box spar. There are actually 2-3 of these spread through the length of the wing section. You can also see where I cut out the foam on the trailing edge and made a 3D printed block holding a piece of bamboo skewer as a locating pin.
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Here's the body of the Duck. Just like the wing panels, there is the original foam box spar with my 3d printed block. There is the same 10mm carbon fiber box tube running through the length of the center wing section. You can also see the matching locating block on the trailing edge. The wing is retained by a 3mm bolt (you can't see it, it's on the other side of the nacelle) that runs through the foam, a 3D printed block, the carbon spar from the outer wing section, and out the bottom. The bottom has a 3D printed part with a captive nylock nut to keep anything from vibrating loose.
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Here's an incredibly crude drawing of the same. The orange lines are the CF spar, the black shaded bits are 3D printed blocks.
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I hope this helps. I think I still have the STL files for the coupling parts if you want to go this route.