EXI and Trex 500 Full Size Tail Servo MOD:
The purpose of this modification is adapt the 500 helicopter to accept a Full Size Tail servo.  A Full size tail servo will have more torque typically than a mini servo. Full Size tail servos are often easier to aquire as well as sometimes less expensive.

NOTE: CF dust is EXTREMELY dangerous. Use a respirator and if possible cut outside. Direct all CF dust into a trash can if possible. CF dust is carcinogenic!

As you can see a full size servo is too big for a 500 bracket.
(click image to enlarge)

The Trex 500 and EXI 500 Carbon eddition come with servo brackets desinged for a mini servo like the Align DS520 and Futaba 9257.  For this helicopter, you can either purchase an Align 600 tail servo bracket then cut it down to fit the 500 bracket or you can take the existing 500 bracket and cut the middle section out and mount the servo just ont he ends.

For the HK500GT or the EXI 500 Plastic version, you need to buy the 500 Servo bracket then do the cut mod or the 500 AND the 600 brackets (this gets expensive).  If you want to just get a 500 Bracket, you can get it from Xheli

This picture shows the difference between a 500 and 600 bracket. You can see that if you have a 600 bracket, you will need to cut the top down a little bit to fit it on the 500 boom bracket.
(click to enlarge)

To cut down a 500 bracket, cut the middle parts out like below:

Then mount the servo, Trial fit the servo and set the servo ball position so that the tail blade pitch is slightly right thrust with the ball at 90 degrees.  Your servo should end up very close to the front of the boom as shown. Note that tape is added to the boom to keep the servo from sliding on the boom. This allows you to not have to over tighten it to keep it from moving on you.