Do those bolts carry all the flight loads?Wel, only if you have tube fuselage fittings .... Most use some sort of channel, I beam, box spar, etc, with the bending strength tailored along the spar to the expected bending moment. And they use bolts to make the connections.
Some of my sketches include large diameter bolt holes where spars pass through fuselage side walls and bolts transfer all flight loads to fuselage walls/bulkheads.
The next question is: what diameter bolts do you need?