The trick with using a morph to do this would be to first create a polygon morph in section for the profile shape you need.
Then extrude or tube it.
Rather than trying to create a solid gutter and then hollowing it out.
However you will probably find it easier to use a complex profile as suggested.
Basically it is the same as it is a profile you extrude.
But being a complex profile, you can tweak the shape easily if you need to.
Barry.
One of the forum moderators.
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