GiantScale, yes, we got your order - thanks! It didn't ask about your Visa because you paid by eCheck direct from your bank account. The reason you didn't see shipping charges is because it's free on orders over $100!
Why do you want to add X4 arms? I would imagine that you could get the lift that you're looking for by removing the part of the chassis below the arms that prevents the arms from moving below the set ride height.