The Plane-Maker from X-Plane v7.x is fun and easy to use... Although I found it a bit limited to edit my planes' fuselage. 20 cross-sections aren't enough, sometimes. It would be nice to export the fuselage shape into any 3D-editor and fine-tune it there... This is exactly what my ACFTools are supposed to do. Please note that X-Plane v8.x is unsupported, unless you create & edit a v7 model and then import it to Plane-Maker v8. But I believe this isn't a problem: X-Plane v8 is able to use OBJ format files (which can be imported/exported by AC3D and Blender plugins) as parts of an aircraft, thus, extremely weird shapes are perfectly possible without even touching the ACF file.
Now, what exactly ACFTools does? It is able to process the file that stores all the aircraft data (except the textures), in the binary ACF format, and dump all the data in the human-readable TXT format. It is the same format as for Tony Gondola's ACF2Text utility, which inspirited my ACFTools. Then, ACFTools can extract the 3D model of the aircraft from this data, and export it in the AC3D format. After that you can edit the aircraft's shape as you want using AC3D and make the inverse process: from .ac to .txt, and then from .txt to .acf. Here comes the brief set of ACFTools features:

• Convert from ACF (aircraft) & WPN (weapon) formats to TXT format and vice-versa.
  
• Extract AC3D model from TXT file, along with wings and propellers (using the real airfoils!).
• Import AC3D model into TXT file (fuselage, nacelles, wheel fairings & external fuel tanks only)
  

3D model extractor is also useful if you want to use X-Plane generated aircrafts somewhere else; as in your own Computer Graphics compositions.
ACFTools was written in Perl, thus it is able to work under Linux, MacOS & Windows. And it is Open-Source & highly modular, so you can modify it as you want, or use my functions for your own needs. When you start ACFTools, this is what you get at your console:
The most important thing you should know is that to convert from the binary ACF format to TXT, ACFTools uses one of the files stored in the defs directory. By default, it is a ACF740.def, which works for X-Plane v7.40 and later. You can specify any definition file you want, as shown on the screen above. You can also write your own definition files, if you have the structure specification. Note that to convert TXT back to ACF, no definition is necessary, as the TXT format itself holds all the data necessary to build the binary file. The second thing is to specify the file that ACFTools should convert. The name of the converted file and every of the intermediary files will be generated from this name. When converting from ACF to AC3D formats, TXT file is generated automatically. Please note that when you want to put the edited aircraft part back into the .acf file, you must save this part as a .ac separate file, then merge it into the TXT file, and after that convert it into ACF! Yes, it would be nice to have a GUI to automate the entire process, but I'm too lazy to do that! Anyway, may the source be with you
I strongly recommend you to read the docs\README.txt file contained in the ACFTools package before you start using it!