My 40' Norman Cross
trimaran has a design
displacement of 8500 pounds. Even allowing for it having been "cruiserfied", I'm sure it still weighs less than half your 22,000 pound figure.
I would guess that your
keel was probably designed by Norman Cross. Many other
trimaran designs, notably Pivers, had keels of his design added. His trimaran keels were lateral resistance devices only, and as such did not have any added weight for ballast.
My
boat uses a 33 pound
Rocna with 50' of 5/16 HT chain as its primary ground tackle. Works well around the
east coast USA and the
Bahamas.