If the surface is properly degreased and you have an adequate close-fitting flat to flat area of contact between the parts to be joined, then I'd say that Sikaflex 512 would do the job very well indeed. It would provide a non-destructive method of making a secure joint that would avoid penetrating the vehicle skin thereby leaving indelible scars. Screws would concentrate all forces on one tiny spot, much as would a rivet, should it come under sudden load then the chances of failure would be high. The aircraft and Formula 1 industries moved away from mechanical fixings and into bonding long ago because highly stressed structures could then spread their loads over big areas and so stay intact in service.
You probably know already that Sikaflex that squeezes out of a joint can be wiped away with Turps / White Spirit while still wet. Should at some time in the future you decide to reverse the exercise, I can report from my own experiences that separating a sikaflexed joint takes quite some doing, but IS possible leaving the original surfaces unmarked. Don't think of it a glorified silicone-sealer.... it's much more adhesive, strong and durable than that.