Sink-Weight. Sounds a bit awkward to me but maybe that's just because it's a term I haven't seen or heard very often. I found the term in an online item about adding weight to a foil and that author cited Jim Michalik's use of the term. So, there it is: Sink-weight and, awkward or not, it is very descriptive.
At any rate, I have installed a 10# sink-weight in Gardens' rudder blade. The weight was poured in a mold and, once cooled, epoxied into a cavity cut into the blade. Two things I didn't like about pouring molten lead directly into the cavity: the possibility of burning/scorching/charring the wood; and, the unknown affect of that much heat on the epoxy holding the blade together (it is an epoxy lamination). Photo shows the dry fit of the sink-weight.
The other component of the rudder assembly, the rudder stock (or head) is being varnished - at least partially for now. The spacers/packers have been glued to one cheek and what will be the interior surfaces are being varnished before assembly (getting to those surfaces once the head is assembled will be terribly inconvenient). Not sure what I'll do for maintenance but I'll figure that out when the time comes.