I've secured the original boxes with a decent, thick cable tie around the adjoining steel bodywork and not had a problem since.
We have to remember that this problem has only arisen later in the cars life due to muck, corrosion & lack of maintenance causing the bonnet latches to become stiff and therefore increasing the load on the splitter.
Take the latches off, strip, clean lubricate and refit, clean and lube inside the original splitter, use a strong cable tie (belt & braces
) and all will be well
