I would think you realize that on your PC you use the very uncommon thing of adding infantry standing to the rear of the tank... 99.9% of the users who will download this model won't be doing that and the tank itself is what should be centered.
The national flag and the selection circle is the measure of what is centered... even in your own screenshot (which is at a 45% angle and down-low... I hope that's not the angle you use to determine centering), you can see the back of the tank inside the circle and the front is sticking out.
To properly view a centering job, you zoom out and above, and compare the national flag and selection circle to your model, as well as comparing it to other properly-centered like-units (in this case properly centered tanks).
As you can clearly see, your tank (especially sans infantry, which is not normal) is not centered... it needs to be moved back.