inverted PCB plug approach (to connect two single sided boards with jumpers)
If I understood correctly, the only mechanical connection between the two boards are the pin of the header. If this is the case, bear in mind that vibrations may be an issue: solder joints, even in through hole mounting, may break if the system is subject to even moderate amount of vibrations.

The problem is that you have sort of a mechanical resonant circuit: the daughter board is like a tank circuit, where the distributed mass of the components and the elasticity of the board behave like L and C.

Without enough damping you may hit a mechanical resonant frequency in the field that may cause your solder joints to break even if the PCBs are not forcefully bent.

That's why, for example, big electrolytic caps (and other bulky components) in power supplies are usually "glued" with silicone compound to the board or to each other. The dampening effect of the cured silicone ensure that vibrations are damped enough not to create problems.

Your idea may work better if you add some additional mechanical element to to strengthen the joint between two boards.