Considering vang attachments,
I had a system once that consisted of a metal
plate that went under foot of the mast (between
the mast and the plate it sits on). It had a
tab that extended aft of the mast an inch
or two that had an attachment point mounted on
it.
Since the attachment point was right under the
goosenect, the boom could move through its range
maintaining constant vang tension.
Since the metal plate was under the mast, holding
it down was just a matter of having an thicker
section of the plate under the mast to keep it
from pulling out.
In any case it seems like something easy to
fabricate. Just something else to think about.
Best wishes,
-greg