The blending is really well done as with most of your art. I know you are aware that the perspective is off, but it adds a new aspect to the picture anyway that is actually really appealing.
Although, the reason i give you an 8 is because even though the picture is AWESOME i would love to see something a bit more than just a tank.
Like an action shot of the tank, whether it be it might have just fired a bullet at something or even just some smoke around the barrel ?
It's upto you but i think you could do something a little more with this image, but i do really like it!