An idea I've considered is buying a large exercise ball and inflating it till it was quite firm. I'd use that as the male mould. Take the female off that one and use it every time I'd need to rebuild the nosecone. Like when my obstacle avoidance sonar failed.Needless to say it wouldn't have any surface patterns, ribs, seams, etc. At least I'd try to get a seamless one. Less work later on to grind off funny lines and "made in China" labels.One consideration is that the ball would probably not be to scale. Could possibly use only part of the arc of the ball for the nosecone. That way the scantlings could be faired into the cone.Rick L.Vancouver