1000 x very many thanks ! I will go ahead along your lines.....Great info !!!
Best regards
Ken

""""find a way to make the various patches continuous between them"""""

Thats the kicker. Thats why that guys nx model said it "wasnt perfect"....

I created the patch in fusion 360 (autodesk gobbled up tools that could do it), but any of the tangency and curvature options would crash the program on the second or third edge pick. The only result was to choose "connected", which is the same as MoI's nsided patch....

The "not perfect" from nx is because the entire surface has to be changed and restructured to achieve the tangency in all directions... forgetting about that bounds center point...

You could do it with alias! Surely they haven't removed the functionality from there...

It will never be perfect, in my opinion not even with Alias, also I have seen them that many go crazy to get surface tangent to an other and sometimes for a simple bevel they take half an hour or more, and they are professionals users, however I found a way to do it with FreeCAD and uses only one nurbs patch, a totally different method from Moi3D but I am already satisfied because I managed to do it with a decent transition now, with the NSIDE command, before it could not execute the command without surfaces.
Below the try with FreeCAD and the control point in Moi3D it's a bit messy

Many thanks Pilou for your input. I was able to install FerrariSketch on WIN 10 - SketchUp 2021
but did not yet succeed to generate the gyroid surface. I think it would help a lot if you could advise me on your
input data with your set up, namely for:
Installing pressure/Warp/Weft tension ratio/Warp orientation/Default edgecable tension/Subdivisions/Accuracy level ???
I assume that the closed boundary has to be treated as rigid ?
By the way this link helped me a great deal to overcome the installation problems !:
https://sketchucation.com/forums/viewtopic.php?f=323&t=32380&p=286311

big thanks for your helping hand
regards
Ken

Yes seems the Ferrari has some little difficulties with this circonvoluted Gyroïd! :)

Many thanks Pilou: would you like to post your gyroid solution ?
Regards
Ken

Little difficulties = no success! (with some number of trys, change parameters etc...

Even with only 2 arcs... :)

Many thanks Pilou, I didn't succeed either with FerrariSketch but the Soap Bubble plugin
worked perfectly, imho...
attached a screenshot + dxf-file of the closed boundary for further testing

regards
Ken