what? so we just want to be bringing the head back and not downwards? every example i've seen of the chin tuck involves bringing the chin in

I thought so too but every  example I've seen has people looking forward. I think mike mew described it as looking down or tucking down for some reason

What about tilting the head upward until the palate/upper dental arch is horizontal? For tongue, jaw and anterior neck muscles this would simulate a forward grown face, allowing them to exert better forces against the palate. Tucking the head in in an upward angle will also engage upper back muscles, giving proper support for the cervical spine, something that can easily be overlooked when the head is tilted down.

Keep in mind that if you have CFD to any degree things will look awkward, but the proper head position can be achieved as follows. Take both your hands, lock them together, reach behind your head until you feel the occipital bone, then, while chin tucking and imagining a puppeteer is pulling up on your occipital bone, lightly push forward with your hands at the bone, counteracting this force with pushing the back of your head upwards and backwards,  until you can feel the back of your neck and occipital bone completely align. You have to be able to take a ruler and have it be touching every part of the back of your neck, no curves. Your chin will most likely be physically intruding on your larynx, and your head will be tilted downwards. It will appear that you are looking downwards, but the key is the train yourself to bring your eyes upwards to look at the horizon while holding it. This is what gives you the "hunters" eyes, there's just a supreme lack of undereye support from the maxilla.

You can look in the mirror to check that you are doing this correctly. You should not be hunching over, and standing completely erect. In fact, your torso should naturally straighten with this maneuver. You will find it exceedingly easy to maintain proper lip, mouth, and tongue posture, and I find that its actually hard to *not* do that in this position.

Another way to do this is to use a wall or your bed with no pillow. I do this before going to sleep and maintain it all night. Simply try to maneuver the back of your head until you can feel your spine from the occipital bone become completely erect, and again, make sure that the back of your neck is completely making contact with the bed/wall. 

The head should be balanced on the weight-bearing part of the spine, on the atlanto-occipital joint between the ears. It should feel poised, free and independent from the spine. And every single vertebra should balance on the one below. You achieve this by learning to release the tension in your body/muscles, especially neck muscles, and letting your skeleton support your whole body. 

Doing so will allow your diaphragm/throat, tongue to rise up as well and be free of tension to function well.

Since the front portion of the skull is slightly heavier than the back portion (looking from the side and in relationship to the ear), it will tend to rotate forwards and downwards a little bit, like a slight chin tuck but without the risk of tension or over doing. 

The person in this picture illustrate what I mean (yes, he is looking down, but he is balanced as well):

i think its pretty thin like i think you should mimick brad pits head posture

@Rockyp33 

Yes, thats a perfect example. He has good facial development so he's not really "tucking" his chin in, but for people like myself with a downswung mandible my face looks much different while maintaining the same posture

Here are my two cents, you should try to get your head back as far back as possible and from that position try to tuck your chin in. The more downwards swung you are the harder this is, I assume it's because at some point you would be completely constricting your airway. I think this is the best way to go about it because pulling your head pack opens up the shoulders and engages the core, moreso than just tilting your head down. So basically make sure that your palate and dental arch is parallel to the ground, then try to pull your head back as far as possible, making sure to squeeze the glutes in as to not have anterior pelvic tilt. In this position, try to chin tuck; I noticed for myself I could barely even move my chin but with this method, you keep trying every day to tuck your chin more and slowly progress. It's basically just progressive overload.

I just tried this and got major tingling down my arms and in my index fingers and thumbs. Anyone else had this?

Yeah happened the first few times!