There is a ball and socket variant that uses the three bolt configuration. With the three fasteners you can have a little misalignment and still tighten it all up.
As for the bolts, it is not the bolt that determines the tightness, it is the nut. If you want a nut that won't back off, then I would suggest scoring some Stover Nuts and using them. The big difference with the Stovers is that they are crimped at one end into a triangular shape that forces the threads to really grab the bolt. They are a one shot deal in that they can only be used once and then have to be replaced but hey, great for security.
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