Hi Don - I’ll see if I can make a coherent blow-by-blow… hold on a bit.
@Don_Sharp - see the attached - I now see your file is V5 and so you don’t have access to the V6 matchSrf options, which are very handy here.
Rhino pipe help_Steps.3dm (934.7 KB)
I see one edge is not well matched - the problem is the green surface is a little too sparsely populated with control points to get a good match - by adding knots (
InsertKnot) in the V (short) direction, with the Automatic option, then
matchSrf one last time, you can get a good match.