you could define them at the begining of user_routines_fast.c after these lines.
Code:
#include "ifi_aliases.h"
#include "ifi_default.h"
#include "ifi_utilities.h"
#include "user_routines.h"
#include "robot.h"
/*** DEFINE USER VARIABLES AND INITIALIZE THEM HERE ***/
So put the variables under where i says define user variables