Sorry for the delay I have been quite busy lately.
This is how I did the top.
pirateofmayhem wrote:when you have a chance, can you post [...] the area around where the back wheels pivot
Here is another view of the area around the wheels I hope it helps.
Also in this picture, notice how the steering is blocked by the front of the engine to prevent the wheels from colliding with the access ramp on the side of the APC. If you clear that 1x2 curved area at the front of the engine, the vehicle could turn a lot faster.