select into composite type / return

I have a function that takes 7 numerical inputs, performs calculations,
and then returns a composite type.

create type breakdown as
  f1    numeric(9,2),
  f2    numeric(9,2),
  f3    numeric(9,2),
  f4    numeric(9,2),
  f5    numeric(9,2),
  f6    numeric(9,2)
);

create function do_breakdown(
  v1 numeric(9,2),
  v2 numeric(9,2),
  v3 numeric(9,2),
  v4 numeric(9,2),
  v5 numeric(9,2),
  v6 numeric(9,2),
  v7 numeric(9,2)
) returns breakdown as $$
DECLARE
  D breakdown;
BEGIN
 -- calculate breakdown
  return D;
END;
$$
LANGUAGE PLPGSQL;

This works great, returning one row with the separate columns.

I now want to set up another function which will take a key, retrieve
the arguments from a table, and call the first function. The problem is
that I can't get the syntax correct to return the composite type.  I
have tried

create function do_breakdown(key text) returns breakdown as $$
DECLARE
  v RECORD;
BEGIN
  select into v * from stored s where key s.key = key;
  RETURN do_breakdown(v.f1,v.f2,v.f3,v.f4,v.f5,v.f6);
END;
$$
LANGUAGE PLPGSQL;

but it returns the whole thing as a single column.  Adding a typecase
didn't help.

I have also tried

create function do_breakdown(key text) returns breakdown as $$
DECLARE
  v RECORD;
  D breakdown;
BEGIN
  select into v * from stored s where key s.key = key;
  select into D * from do_breakdown(v.f1,v.f2,v.f3,v.f4,v.f5,v.f6);
  RETURN D;
END;
$$
LANGUAGE PLPGSQL;

but that also returns everything as a single column.  Any help would be
appreciated.

Gary