no specific example, just a tale.
when we where updating Orbital Tug, I wanted to add a new version of a single part 'helperDrone' - great little part - self contained drone with RCS, grabber, light, and reaction wheel - totally a drone. This version was going to integrate the TACSelfDestruct part - so it could be used as a demolitionHelperDrone (blow up space debris etc).
I could have just copied the helperDrone.cfg and added the TACSelfDetruct module to it, but I also wanted it to look like Val had strapped on several blocks of explosives, and remote control detonation controller (both parts in the TACSelfDestruct mod).
So I created a new part.cfg file and copied the original base part into it. I then added the TACSD module into the parts configuration code. In order to get the final look, I created in the VAB a helperDrone and surface attached the parts I wanted to be there (weld). I kept it simple.
I saved that as a .craft file, and opened the .craft in a text editor and found the individual parts and copied their PosX, PoSY, PosZ, RotX, RotY, RotZ
I wanted four parts welded to the base (3 of the same X-1100 and one twsa_bomb)
since I used +PART (copy part) everything from the original part was there (or you can just copy the entire part.cfg and modify)
(REMEMBER: change the part name to something different)
I then copied the MODEL (or mesh) from the parts I wanted to weld - and adjusted the position/rotation (scale is optional - leave off unless you need it or get much better) into the new part.
then it was quite a bit of mucking about to get them just right - (nodehelper helps) - which required restarted the game (or reloading the database) numerous times.
That's it. (Autoweld does more - but this is the 99 class on manual welding)