Hi,
Thank you for your encouragements. It's been a pleasure to build this vehicle, it is getting close to the end of the building phase.
Here is some more info on the electronics and gears i am using. I am no expert on electronics but many builders are likely facing the same situation, first time with wheeled vehicle... Can't put a Heng Long or Clark control board on these.
Requirements:
- Replace the basic WPL remote, electronics and the directional gizmo by something better
- I do not like car remote controls with the wheel and pistol grip, i prefer the 2 sticks
- Need to rotate the turret and gun elevation
- Head and tail lights
- Engine sound
- Machine gun sound and flash (dropped)
An extra flysky receiver for my RC unit can be purchased for $20. It is cheap enough to be purchased and left permanently in the vehicle, well until that time when you need one asap...

- Flysky IA10B receiver
Individual WPL servo of the right size can be purchased for less than $10, mostly to cover shipping... It provide a very smooth and precise control of the vehicle compared to the gizmo the M35 came with.

- WPL servo
A 10A Bustophedon ESC Brushed Speed Controller can be purchased for $4 including shipping. There are 20A and 30A versions available of this model and I will later experiment with these. Can be hooked to the 6V battery and motor of the WPL M35 by connecting directly or changing the connectors. Another one will also be used to control the Heng Long turret rotation unit, with variable speed and reverse, it seems to work fine in tests.

- 10A Bustophedon ESC Brushed Speed Controller
Sold on eBay for $24, this RC car truck sound unit provide 2 speakers and selection for 10 different sounds. Although most of them seemed to be airplanes (??) and racing cars engines, one of them is obviously a large truck engine and is close enough. It has engine start, idle and acceleration. It connect to the same RC channel as the speed control through a Y splitter. I will only install one speaker so I have an extra one for another project.

- RC Car Truck Engine Loud Sound Module
LED unit, can be purchased for $1, shipping included. Connects directly to the receiver.

- Car 5mm 4 LED
On a tip from Carl on his M3 build, I purchased a Vex Gear Kit, mine at Robotshop.com for less than $20 including shipping. A medium size wheel will simply be put under the turret and it fits the gear of the Heng Long rotation unit. Enough for many vehicles. A small servo will sit on the wheel for gun elevation.

- Vex Gear Kit
I dropped the requirement for gun flash because the Aber barrels do not have a bore. As I needed to make a choice, I preferred accuracy than sound. There are some RC airplane machine gun sound units available on specialized websites but I did not think it was worth the cost.
Regards, Louis