Custom System Target variables

This might be a rather small detail but I have created a custom system target file and I have two questions regarding it: 1) How can I change the name of the generated main file. I modified the ert tlc/make files to create my target and now upon generation my main file is called ert_main.c. I would like this to be a different name but I cannot find a place where it is defined.

2) I am trying to use the solver "Fixed step size" variable in my generated code but once again I cannot find where it is specified in the tlc file.

Any help will be appreciated!