Very basic fading edge patch layout; matching G2 lengthwise, with the “Preserve isocurve direction” option on, nevertheless sees the matched surfaces jump off their long edges, and G0 continuity is lost. The exact same surfaces aligned G2 in Alias (IGS export) remain G0 continuous, keep to their edges. Why is this?
Matching G1, with the “Preserve isocurve direction” option on, and some time consuming CP noodling (that should not be necessary) does work.
Apparently, this is a 12 years old bug 
Hopefully @menno gets to work on matchsrf in the near future.
it needs a lot of love.
fwiw, patch in v9 may be the best tool in Rhino to do this type of work going forward.
fwiw in the level 2 manual there are 2 lessons for making fading creases that do actually work with matchsrf in its current state. not arguing this is better than what alias has, but it’s worth taking a look at.
This has been requested gazillion times during the years… The two most important NURBS modeling tools, “Blend surface” and “Match surface”, both saw just a minor love since Rhino 4 (released in February 2007). If memory serves me right, Rhino 4 added the ability to rotate the individual handles of the blend surface. That was the last major feature added to these tools.
Rhino 5, Rhino 6, Rhino 7, and Rhino 8 focused on other tools. If Rhino 9 also doesn’t fix that bug, that will make more than 3 decades of ignoring it. 
That’s the problem with the “Swiss Army knife” approach to product development. The “Preserve isocurve direction” option is so very essential and should just work.
