Mount questions

When I mount an fxStaticSprite2D 'A' on another 'B' and set the mountForce to 0 so they move toghether, but when I move B with setLinearVelocityX, A starts to get a little behind, it's just a couple of pixels, but it does sepparate from A, maybe it's because I keep changing setLinearVelocityX because I want to acomplish an accelerated movement. So anyways, my question is if there's any way I can them to move toghether with mount? because right now I discarded the mount function and am using setLinearVelocityX on both objects, so they move side by side.

Another mount questions, when I mount an object how can I rotate it?

And last question... but not a mount question... is there any way to move the pivot point of a fxStaticSprite2D? or does it always rotates from the center of the image?

Thanks a lot