Bikepacking - a viable alternative to racks & panniers

Yeah, in the downwards direction onto the seatpost. The saddlebag would be pulling the rear parts of the rails, which aren't designed to be clamped (they are a different shape). The more I think about it the more it should be ok. Ultimately the saddle has a limit of 100kg and all I want to do is hang another 5kg or less off it. I'll just wrap some tape over the rails to prevent any rubbing.