I have spent lots of time lying over bricks! It has made a huge difference in the mobility of my upper spine. Pressing your legs down creates more space and freedom in the spine, as it does in standing poses. Good practice here, because you can press the whole back of your leg down!
At first, I needed extra head support, because my back would not arch over the brick between my shoulder blades. Your neck should not feel jammed or uncomfortable and no dizziness - take what head support you need until you develop the ability to arch back. Some may need to start on a lower brick. Keep the brick between your shoulderblades - not under the waist or lower back.
