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.
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