Change the Size of Pipe Tap (Welded Outlet)

Hi everyone!

I’m having hard times while trying to change the Nominal Size of the Tap. It works fine when the pipe is still connected to it (I can do it changing pipe size). In my case I have removed the pipe and have a sprinkler instead. Is there a way to workaround this? I mean…change the tap size without having a pipe anymore.

I have tried Dynamo already, but since the Nominal Radius of the tap is Read Only my hands are tied.
Any ideas? Anything helps.