Physics and parameters in Galactic CR transport models

There are several codes available that numerically model the propagation of Galactic cosmic rays in our Galaxy. Each of these tackle this problem in different ways and concentrate on different aspects of the propagation. For the modelling of γ-rays detectable at Earth, however, GALPROP appears to be the most widely used numerical model. The reason for this is due to the fact that it considers a huge variety of effects that affect the propagation of the particles and γ-ray production. This wealth of included physics results in two principle caveats: On the one hand results depend on a vast amount of static parameters, therefore inviting to fit the data by tuning - occasionally resulting in degenerate physical conditions. On the other hand often physical effects are masked by these parameters. We will scrutinise the implementation of different physical aspects in the current GALPROP framework. We contrast this by presenting own developments and give some specific examples.