diff --git a/src/Makefile b/src/Makefile
index b36e6d431..c2ddf89e4 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -98,9 +98,15 @@ AUDIO = NO
 VOICE = NO
 
 # corrects different rounding for negative values. So instead of -99.9 you will see again -100.0
-CORRECT_NEGATIVE_VALUES = NO
+# Values = YES, NO
+CORRECT_NEGATIVE_VALUES = YES
+
+# adds additional code to prevent arithmetic overflows. MAX or MIN values stays. Not yet guaranteed!! Just improved
+# Values = YES, NO
+ARITHMETIC_OVERFLOW_CHECK = NO
 
 # increases range of expo curve but costs about 82 bytes flash
+# Values = YES, NO
 EXTENDED_EXPO_CURVE = NO
 
 # HAPTIC Mods
@@ -420,6 +426,10 @@ ifeq ($(CORRECT_NEGATIVE_VALUES), YES)
   CPPDEFS += -DCORRECT_NEGATIVE_SHIFTS
 endif
 
+ifeq ($(ARITHMETIC_OVERFLOW_CHECK), YES)
+  CPPDEFS += -DPREVENT_ARITHMETIC_OVERFLOW
+endif
+
 ifeq ($(EXTENDED_EXPO_CURVE), YES)
   CPPDEFS += -DEXTENDED_EXPO
 endif
diff --git a/src/myeeprom.h b/src/myeeprom.h
index 3a30457e1..3a794d27d 100644
--- a/src/myeeprom.h
+++ b/src/myeeprom.h
@@ -73,8 +73,10 @@ typedef char gvar_name_t[6];
 #define GVAR_MAX  1024
 #endif
 
+#define RESERVE_RANGE_FOR_GVARS 10
+// even we do not spend space in EEPROM for 10 GVARS, we reserve the space inside the range of values, like offset, weight, etc.
 #if defined(CPUM64) && defined(GVARS)
-  #define MAX_GVARS 9
+  #define MAX_GVARS 5
   #define MODEL_GVARS_DATA gvar_t gvars[MAX_GVARS];
   #define PHASE_GVARS_DATA
   #define GVAR_VALUE(x, p) g_model.gvars[x]
@@ -83,7 +85,7 @@ typedef char gvar_name_t[6];
   #define MODEL_GVARS_DATA
   #define PHASE_GVARS_DATA
 #elif defined(GVARS)
-  #define MAX_GVARS 9
+  #define MAX_GVARS 5
   #define MODEL_GVARS_DATA gvar_name_t gvarsNames[MAX_GVARS];
   #define PHASE_GVARS_DATA gvar_t gvars[MAX_GVARS]
   #define GVAR_VALUE(x, p) g_model.phaseData[p].gvars[x]
diff --git a/src/open9x.cpp b/src/open9x.cpp
index 727805925..a39c12abb 100644
--- a/src/open9x.cpp
+++ b/src/open9x.cpp
@@ -658,7 +658,7 @@ void applyExpos(int16_t *anas)
 
 #if !defined(CPUARM)
 
-#define CORRECT_NEGATIVE_SHIFTS
+// #define CORRECT_NEGATIVE_SHIFTS
 // open.20.fsguruh; shift right operations do the rounding different for negative values compared to positive values
 // so all negative divisions round always further down, which give absolute values bigger compared to a usual division
 // this is noticable on the display, because instead of -100.0 -99.9 is shown; While in praxis I doublt somebody will notice a 
@@ -666,6 +666,7 @@ void applyExpos(int16_t *anas)
 // this define would correct this, but costs 34 bytes code for stock version
 
 // currently we set this to active always, because it might cause a fault about 1% compared positive and negative values
+// is done now in makefile
 
 int16_t calc100to256_16Bits(int16_t x) // return x*2.56
 {
diff --git a/src/open9x.h b/src/open9x.h
index ddd1fa49f..2b489b83e 100644
--- a/src/open9x.h
+++ b/src/open9x.h
@@ -825,16 +825,9 @@ void incRotaryEncoder(uint8_t idx, int8_t inc);
     #define GV1_LARGE  256
   #endif
 
-  // depends if we want free ranges for use, if no MAX_GVARS are smaller
-  // if not this would assume a max for GVARS instead using MAX_GVARS
-  #define GV_RANGESMALL      (GV1_SMALL - (MAX_GVARS+1))
-  #define GV_RANGESMALL_NEG  (-GV1_SMALL + (MAX_GVARS+1))
-  #define GV_RANGELARGE      (GV1_LARGE - (MAX_GVARS+1))
-  #define GV_RANGELARGE_NEG  (-GV1_LARGE + (MAX_GVARS+1))
-  
   #define GV_IS_GV_VALUE(x,min,max)    ( (x>max) || (x<min) )
   #define GV_GET_GV1_VALUE(max)        ( (max<=GV_RANGESMALL) ? GV1_SMALL : GV1_LARGE )
-  #define GV_INDEX_CALCULATION(x,max)  ( (max <= GV1_SMALL) ?  (uint8_t) x-GV1_SMALL  : \
+  #define GV_INDEX_CALCULATION(x,max)  ( (max<=GV1_SMALL) ? (uint8_t) x-GV1_SMALL  : \
                                        (  (x&(GV1_LARGE*2-1))-GV1_LARGE ) )
   #define GV_INDEX_CALC_DELTA(x,delta) ((x&(delta*2-1)) - delta)
 
@@ -846,17 +839,13 @@ void incRotaryEncoder(uint8_t idx, int8_t inc);
   extern uint8_t s_gvar_last;
 #else
   #define GET_GVAR(x, ...) (x)
-
-  // can be used also without GVARS for allowed parameter ranges (makes -500 +500 range for weight unneccessary)
-  // do we want to allow wider ranges without GVARS? Would cause a conversion problem later on, a lot of options needs to be check to do it right
-  #define GV1_SMALL  128
-  #define GV1_LARGE  256
-  #define GV_RANGESMALL      (GV1_SMALL-1)
-  #define GV_RANGESMALL_NEG  (-GV1_SMALL+1)
-  #define GV_RANGELARGE      (GV1_LARGE-1)
-  #define GV_RANGELARGE_NEG  (-GV1_LARGE+1)  
 #endif
 
+#define GV_RANGESMALL      (GV1_SMALL - (RESERVE_RANGE_FOR_GVARS+1))
+#define GV_RANGESMALL_NEG  (-GV1_SMALL + (RESERVE_RANGE_FOR_GVARS+1))
+#define GV_RANGELARGE      (GV1_LARGE - (RESERVE_RANGE_FOR_GVARS+1))
+#define GV_RANGELARGE_NEG  (-GV1_LARGE + (RESERVE_RANGE_FOR_GVARS+1))
+
 extern uint16_t s_timeCumTot;
 extern uint16_t s_timeCumThr;  //gewichtete laufzeit in 1/16 sec
 extern uint16_t s_timeCum16ThrP; //gewichtete laufzeit in 1/16 sec