several times i come across similar issues like the one (a reduced / simplyfied version) you find attached.
how to fill the hole between the surfaces with a G2 surface / surface combination?
In the .3dm file you will find a t-spline - solution.
rhino patch fails.
i managed to get some acceptable but painful solutions with some of the blend commands.
looking for a pure rhino-commands-solution. - or a link to similar, solved problems
handleConnection_02.3dm (2.1 MB)
thanks, best, Tom