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Henlong Panzer III with Battle Circuit
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The Tamiya TBU mounts easily in the commanders cupola without too much cutting up. I trimmed the base of the TBU to fit within the bottom half of the cupola and used hot glue to secure it. 
 
Keep in mind the TBU needs to face a certain way so when mounting it you need to be sure on the unit's facing. Double check before glueing anything.
I replaced the red LED with the infrared LED. This will have a wide pattern by the way it sticks out, you can use some plastic tubing to narrow the beam spread. Use a few of my target ciruicts to test, simply line them up and shoot at them and see how the beam spreads as you get further away.
 
Since this will most likely be my "guest" tank I will give them an advantage with a large spread.
Yup another wiring mess! The battle circuit sits nicely above the battery compartment. Of course I cut the bottom of the airsoft gun assembly off. No BB firing for this tank, only infrared combat!
 
Below the RESET button and master power switch are mounted at the rear of the tank.
Here you can see that the bottom section of the airsoft gun has been cut away. The wires from the Tamiya TBU and the infrared LED run from the turret out.
The red circle shows where I tapped into the Henlong board for triggering the Battle Circuit to fire. When the gimbal for firing on the radio is pushed forward this pin goes high. This can be wired directly to the trigger input.
 
To the right below is where the output from the sound module is connected. I used a 1uF capacitor between the output of the sound module and this connection to the Henlong board. This is the input to the Henlong's audio amplifier.
The installation was easy. I found a point on the Henlong circuit board to trigger the Battle Circuit to fire and also was able to tap into the audio circuitry. I decided to keep the original electronics and radio. The only part I removed was the airsoft gun, or a portion of it. That was necessary to mount the Battle Circuit, and besides I wasn't going to use the BB firing capabilities anyway. 
I will probably use a separate audio amp for the hit and firing sounds. The problem I encountered is on the last hit when the tank is shut off there is no "hit: sound because the power to the tank is cut off be the relay. A separate audio amp on its own power will alleviate this.