diff --git a/config.h b/config.h
index c0f9ad6..72aad6f 100755
--- a/config.h
+++ b/config.h
@@ -27,6 +27,7 @@
 #define BAUD_RATE 9600
 
 // Define pin-assignments
+// NOTE: All step bit and direction pins must be on the same port.
 #define STEPPING_DDR       DDRD
 #define STEPPING_PORT      PORTD
 #define X_STEP_BIT         2  // Uno Digital Pin 2
@@ -44,6 +45,7 @@
 #define STEPPERS_DISABLE_BIT    0  // Uno Digital Pin 8
 #define STEPPERS_DISABLE_MASK (1<<STEPPERS_DISABLE_BIT)
 
+// NOTE: All limit bit pins must be on the same port
 #define LIMIT_DDR       DDRB
 #define LIMIT_PIN       PINB
 #define LIMIT_PORT      PORTB
@@ -76,6 +78,7 @@
   #define COOLANT_MIST_BIT   4 // Uno Analog Pin 4
 #endif  
 
+// NOTE: All pinouts pins must be on the same port
 #define PINOUT_DDR       DDRC
 #define PINOUT_PIN       PINC
 #define PINOUT_PORT      PORTC
@@ -135,7 +138,7 @@
 // round-off can be great enough to cause problems and/or it's too fast for the Arduino. The correct
 // value for this parameter is machine dependent, so it's advised to set this only as high as needed.
 // Approximate successful values can range from 30L to 100L or more.
-#define ACCELERATION_TICKS_PER_SECOND 60L
+#define ACCELERATION_TICKS_PER_SECOND 50L
 
 // Minimum planner junction speed. Sets the default minimum speed the planner plans for at the end
 // of the buffer and all stops. This should not be much greater than zero and should only be changed
@@ -169,6 +172,32 @@
 // ---------------------------------------------------------------------------------------
 // FOR ADVANCED USERS ONLY: 
 
+// The number of linear motions in the planner buffer to be planned at any give time. The vast
+// majority of RAM that Grbl uses is based on this buffer size. Only increase if there is extra 
+// available RAM, like when re-compiling for a Teensy or Sanguino. Or decrease if the Arduino
+// begins to crash due to the lack of available RAM or if the CPU is having trouble keeping
+// up with planning new incoming motions as they are executed. 
+// #define BLOCK_BUFFER_SIZE 18  // Uncomment to override default in planner.h.
+
+// Line buffer size from the serial input stream to be executed. Also, governs the size of 
+// each of the startup blocks, as they are each stored as a string of this size. Make sure
+// to account for the available EEPROM at the defined memory address in settings.h and for
+// the number of desired startup blocks.
+// NOTE: 50 characters is not a problem except for extreme cases, but the line buffer size 
+// can be too small and g-code blocks can get truncated. Officially, the g-code standards 
+// support up to 256 characters. In future versions, this default will be increased, when 
+// we know how much extra memory space we can re-invest into this.
+// #define LINE_BUFFER_SIZE 50  // Uncomment to override default in protocol.h
+  
+// Serial send and receive buffer size. The receive buffer is often used as another streaming
+// buffer to store incoming blocks to be processed by Grbl when its ready. Most streaming
+// interfaces will character count and track each block send to each block response. So, 
+// increase the receive buffer if a deeper receive buffer is needed for streaming and avaiable
+// memory allows. The send buffer primarily handles messages in Grbl. Only increase if large
+// messages are sent and Grbl begins to stall, waiting to send the rest of the message.
+// #define RX_BUFFER_SIZE 128 // Uncomment to override defaults in serial.h
+// #define TX_BUFFER_SIZE 64
+  
 // Toggles XON/XOFF software flow control for serial communications. Not officially supported
 // due to problems involving the Atmega8U2 USB-to-serial chips on current Arduinos. The firmware
 // on these chips do not support XON/XOFF flow control characters and the intermediate buffer 
diff --git a/limits.c b/limits.c
index f34ffbd..bc0cf40 100755
--- a/limits.c
+++ b/limits.c
@@ -33,6 +33,7 @@
 #include "limits.h"
 #include "report.h"
 
+#define MICROSECONDS_PER_ACCELERATION_TICK  (1000000/ACCELERATION_TICKS_PER_SECOND)
 
 void limits_init() 
 {
diff --git a/limits.h b/limits.h
index a904ac9..847c667 100755
--- a/limits.h
+++ b/limits.h
@@ -21,8 +21,6 @@
 #ifndef limits_h
 #define limits_h 
 
-#define MICROSECONDS_PER_ACCELERATION_TICK  (1000000/ACCELERATION_TICKS_PER_SECOND)
-
 // initialize the limits module
 void limits_init();
 
diff --git a/planner.h b/planner.h
index 37bd188..b0fffa6 100755
--- a/planner.h
+++ b/planner.h
@@ -23,7 +23,9 @@
 #define planner_h
                  
 // The number of linear motions that can be in the plan at any give time
-#define BLOCK_BUFFER_SIZE 18
+#ifndef BLOCK_BUFFER_SIZE
+  #define BLOCK_BUFFER_SIZE 18
+#endif
 
 // This struct is used when buffering the setup for each linear movement "nominal" values are as specified in 
 // the source g-code and may never actually be reached if acceleration management is active.
diff --git a/protocol.h b/protocol.h
index 83c4c0d..209d19d 100755
--- a/protocol.h
+++ b/protocol.h
@@ -29,7 +29,9 @@
 // characters. In future versions, this will be increased, when we know how much extra
 // memory space we can invest into here or we re-write the g-code parser not to have his 
 // buffer.
-#define LINE_BUFFER_SIZE 50
+#ifndef LINE_BUFFER_SIZE
+  #define LINE_BUFFER_SIZE 50
+#endif
 
 // Initialize the serial protocol
 void protocol_init();
diff --git a/serial.h b/serial.h
index 3ea56c0..3ffde2e 100755
--- a/serial.h
+++ b/serial.h
@@ -27,8 +27,13 @@
 
 #include "nuts_bolts.h"
 
-#define RX_BUFFER_SIZE 128
-#define TX_BUFFER_SIZE 64
+#ifndef RX_BUFFER_SIZE
+  #define RX_BUFFER_SIZE 128
+#endif
+#ifndef TX_BUFFER_SIZE
+  #define TX_BUFFER_SIZE 64
+#endif
+
 #define SERIAL_NO_DATA 0xff
 
 #ifdef ENABLE_XONXOFF
diff --git a/stepper.c b/stepper.c
index 56350cc..129ccd8 100755
--- a/stepper.c
+++ b/stepper.c
@@ -28,6 +28,9 @@
 #include "settings.h"
 #include "planner.h"
 
+// Some useful constants
+#define TICKS_PER_MICROSECOND (F_CPU/1000000)
+#define CYCLES_PER_ACCELERATION_TICK ((TICKS_PER_MICROSECOND*1000000)/ACCELERATION_TICKS_PER_SECOND)
 
 // Stepper state variable. Contains running data and trapezoid variables.
 typedef struct {
diff --git a/stepper.h b/stepper.h
index 84fe8c0..0cb4189 100755
--- a/stepper.h
+++ b/stepper.h
@@ -24,10 +24,6 @@
 
 #include <avr/io.h>
 
-// Some useful constants
-#define TICKS_PER_MICROSECOND (F_CPU/1000000)
-#define CYCLES_PER_ACCELERATION_TICK ((TICKS_PER_MICROSECOND*1000000)/ACCELERATION_TICKS_PER_SECOND)
-
 // Initialize and setup the stepper motor subsystem
 void st_init();