On Mar 31, 12:15 pm, Martin Pentreath
wrote:

My idea on building one is to build a steel framed box about 1m high
with a random taper ff each side.
Then to cover this with chicken wire and bend to shape. Once happy, I
can cover with some mortar and rocks.

Why not get a large block of polystyrene foam? Lighter and cheaper
than steel, and it won't go rusty. Hack into the shape you want and
cover with chicken wire and cement.