After looking at my library of Hunt photos. I Notice the Sonar dish, which is stored on the bridge front, was different to the drawings. The actual dish is not a dome shape as shown on the drawing ,but more like the dome has had its side squared off.(see attached photo)
So I decided the best way to make it was to cut the round base from 2 mm plastic card, then cut the cross section shape from 10 thou card. This was then attached to the base and filed using P38 filler, then i sanded it to the correct shape.