Hi Michael, now you've provided me with a lot of knowledge and I thank you very much! I sat down to make an image so I could show you what it is I'm trying to do, and now I feel like a complete idiot...

Last night I tried this but it took forever and ever and still no shell. Must say that MoI performs excellent in these cases, it doesn't hang or freeze, it just calculates and if you wish to abort you just click cancel. This is great.
I believe it was rather my laptop that was tired last night. But now it works. This is what I've tried to do all the time.

I cannot join the two halves, left and right, but MoI could still create a centerline shell. The maximum shell thickness is 0,25

Will try the Network command, that together with the sweep tecnique you showed me would possibly give me more control over the way the edges look.

/Lars