This is a simple mod for the TH8A to mimic cars with reverse lock out to not engage reverse accidentally.

This version is for use with the original metal gear/gate plate.

*** This one will not work on the TH8S ***
 

Additional parts you will need:
1 - Qty 1 - spring 0.4mm, 50mm, 10mm (0.4mm wire thickness/diameter, 50mm spring length, 10mm spring diameter)

       (The wire thickness/diameter can be larger for more resistance but this works just fine for me as it's what I had lying around. 
       I got mine here : [https://a.aliexpress.com/_mNLG1H3](https://a.aliexpress.com/_mNLG1H3)

2 - Qty 2 - M3 screws 30mm length

Print Settings:
The pull up Knob and knob retainer have XY hole compensation set to 0.125
The cylinder/gear blockers have XY hole compensation set to 0.250

Installation:
The file has two small cylinders.
The shorter cylinder goes on the rear right side for reverse (8th gear position / far lower right).
The tall cylinder goes on the front left side for Euro car style reverse (1st gear position / far upper left).
 

1 - Install just one of the cylinders depending on which gear pattern you need. Use the new M3 screws for these. 

     Both cylinders go installed with the slanted part facing down (The recessed M3 hole facing upward), taller side outward, to make up for the curvature of the gear/gate plate.
2 - Replace the shaft bushing with the one here with the lip section upwards and screw the shaft back in place.

3 - Drop in the Pullup knob.
4 - Drop in the spring.

5 - Screw on the knob.

When you need to engage reverse just pull up on the knob to get over the stopper/cylinders to get into reverse. 

For Euro style you can use gear blocker to completely block 2nd gear.
For regular 6 + R you can use a gear blocker to completely block 7th gear.
 

Notice the red cylinders with slanted side facing down and tallest side facing outward.

You would only use one reverse gear blocker at a time. here I had both for the example.