I owned an Iroquis Mk II in the early 1970's, this was the 30 foot version with transom hung rudders. I bought a shell from the builder Reg White of Sailcraft in Brightlingsea, England and fitted it out, never finished though - got married instead (mistake). I sailed other Iroquis around this time however, best speed was 18 knots, nice boat. E-mail me if you wany any specific info terry@tndavis.co.uk