Part modding, help required

[TheFluffiestThing]

Hi,

This is my first attempt at part modding in KSP beyond making empty tanks. I want to alter the fairings found in the KW rocketry pack, so that as well as being able to use the nosecone to top the fairing, I can also use a fairing base then continue with the rocket like this:

So far I've added a new part which uses all of the data for the original fairing wall with a modified part file which changes the attachment node for the wall part to be attached to the upper fairing base. Here is a screenshot of the original part file:

And here is the new part file:

Here is an in-game side by side comparison of the two parts:

The attachment points are in the right place, after a little trial and error. I know it's a rather crude job and the parts will clip, but it's the best I can do without re-texturing. The problem I am having is that the decoupling node which I have added is not working properly as it only removes the bottom wall and not the top one. Does anyone know how to make this work?

Cheers