This was a quick experiment with tubular monostays riveted into the structure. I didn't really do any strength calculations on this; I include it here just to record the idea for posterity. Here is an overall view:Zooming into the attachment area and removing the side skin, we have:
After we remove a couple more parts, we can see the tubes nestled in there:
This design assumes that each tube is attached by a line of rivets on each of 3 sides (top, bottom and outboard) to achieve the necessary strength.