Had a really helpful phone call from Mike (?) of u-marq who gave me some good advice on using clearing toolpaths, and put me right on something I had been doing wrong for years. So hopefully I will not have any more issues with the nose cone dropping into the gap.
I suppose it's one of the problems with being mostly self taught on these machines, you don't always realise that there's a better way to do something. But it's nice to know that u-marq are keeping an eye on this thread and will phone to give advice if they think it's needed.