Very nice metal work there Gato !

With respect to the hole on the bottom of the beam. Because of the dolphinstriker and upward pretension of the beam you don't really need the material there. The beam is mostly under direct compression and with the right upward prebend the beam bends down under sailing loads to almost hardly any bending stresses. This is why the "tube through bottom of mainbeam" as the dolphinstriker pin is such a common way of fitting. It is simple, does the job very well as it transmits the loads directly from the pin to the mast voet and it doesn't crack up or break even after years of usage. There is not much point in doing it any other way.

Wouter