If you do not want to spend Euros to get a post for this Centroid then what you should do is take one the default combinations (in the GppToool directory) of mac and gpp and generate some g-code and see how close it is to what you need. From there you will need to go into the mac and gpp files and make the necessary changes. There are instructions and samples if with SolidCAM open you click on Help/SolidCAM Help Topics/GppTool
This tweaking of post processors is not to difficult for simple stuff but can get fairly complex as you start getting beyond the basics of driving your machine toool. I would consider the basics of driving the machine tool to be setting coordinate systems, turning spindle on/off, making rapid moves, turning on/off tool length compensation, turning on/off cutter compensation, 2 and 3 axis profiling/contouring/pocketing, using drilling/boring/tapping cycles, simple subprograms, moving to home when done, and so on. From a post processor standpoint when you get to complex subprograms, 4/5 rotational/indexial, simultaneous, and so on it can become difficult and very time consuming.
If you don't want to mess with any of this in most places you can hire your reseller or SolidCAM to do it for you.
This was covered in more detail in another thread "What controller do I use, is FUNUC defaut?"