Welding Method Collaboration

[MrRadicalEd]

So I after many hours of vanilla KSP, I've decided to use a few choice mods and I wanted to learn how to weld parts together. I was thinking of an "easy" and intuitive way to do this.. despite some great efforts, the instructions out there are not friendly to the uninitiated.

I wanted to see if I could mock up a part as a model in the VAB first, and then convert it to a welded part. I'd like some help to understand this and develop a technique for us all to do it at our leisure. I can get models loaded in to the VAB as a single PART, but the orientation and attachment points are not correct. If this can be perfected, we would have a rather intuitive way to assemble and then weld these things!

First, here is a model I saved that I want to fuse as one piece.

Second, here is the mostly converted welded part that has attachment point and orientation issues. The parent attachment point should be this Micronode part or one of those girders next it. all those Girder Segments should be horizontal with the floor connected to each adjacent part.

Left: Welded Part, Right: Model of parts

So far.. we can build our to-be-welded part in the VAB for the most part, but what is the process to take our saved model and convert it to a welded part?