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While waiting for Mr. B to return, here’s a method using only native tools that can be done with any version of Sketchup. Working from the left:
1.Place tube components as needed. Let the tube being coped be plenty long. The waste side won’t cost anything and you won’t be filling the scrap bin.
2. Open the tube that isn’t getting coped and copy the outside surface to the clipboard with Ctrl+C (Command-C on Mac). Close this component to get out of Edit mode (use Esc). Then hide that component to get it out of your way for the moment. Open the other component which is getting coped and use Edit>Paste in Place to paste the copied surface.
3. Select the surfaces, right click and choose Intersect Faces>With Selected. Edges will be formed between the crossing surfaces.
4. Erase the tube on the waste side of the cope along with the surface from the other tube. Correct the face orientation in the coped area.
5. Unhide the other tube.