Wow. That is... not like my mast bases at all. I'll see if I can load the pictures up tonight. Bottom line, my mast base is octagonal like the picture above, but there is a saddle right down the middle. My mast heel casting has a corresponding cutout in the base to register the rotation of the mast (within a couple of degrees). I have tie-down straps (two each), but they are straps, not wire, and they screw into the mast. Finally, my mast bases do not have a clamp or jump pin or lug or whatever that step 2 is, but rather has four screws that don't quite penetrate the mast heel that seem to be there to center the mast heel and keep it from moving around.
As I say, I'll see if I can remember to post some pictures tonight.
Brian
SV Serenity
Nonsuch Nereus #003
Pax River MD