Hello Elder and Audi,
If I may interject, about the "tongue" touching the upper palate practice....
This is a "circuit" to complete the Macroscosmic and Microscosmic orbit practice within the higher levels of Chi Kung and Nei Kung practice as part of the disseminating Chi along the meridians throughout.
After learning the typical....Dan Tian breathing and bone breathing...Thru Nei Kung, one can practice this to complete the circulation of the CHI throughout the body. The "tongue" is the main switch, activating the FRONT side and the BACK side of the meridians. Although, Audi proposed a "practical" function of the tongue being "tucked" away to prevent injury while fighting is also a novel concept and functional one.
But it is more about the "internal" circuitry that reveals more of NEI KUNG's higher and more sophisticated dissemination of CHI following our Yi or I (will). Completing the Microscosmic orbit first (upper body excluding the legs) then graduating to the Macroscosmic orbit (upper and lower body) would lend our I or Yi to lead the CHI with utmost command that applies to health and martial applicaton.
The health application is the concentration of CHI on key meridian spots as you circulate along the orbit while the dissemination of CHI martially is of utmost and "higher" level of command...for example, on a WARD OFF, the CHI from our Dan Tian is sent to the legs and our soles and let it ride up again to our waist and thru the spine to our uppers limbs and the head and then recycling the CHI back to our Dan Tian without losing CHI. The key is this Orbit is really a supplementary practice within Chi Kung and ultimately NEI KUNG only after we have compressed YIN/YANG in our DAN TIAN after much sitting and standing meditations.
Again, the application of movements is to enhance the movement of the CHI initiated by our YI or I but eventually, it is just our minds.
To read more about this orbit practice, read from MANTAK CHIA who wrote extensively in this matter. Dr. Jwi Ming (spelling unsure) also emphasize this one)
Other practice on stillness meditation override this practice because the stilness meditation starts from Dan Tian and eventually "leak out" to different meridians and cavities and finally "opening" up all meridians and distributing it efficiently.
The key is that the DAN TIAN is the source of CHI where it is stored initially through NEI KUNG postures and stillness practice, then assimilating it with CHI KUNG (breathing) and movement where CHI will be moved to different parts of the body.
There is a "higher" practice than this one...it is the moving of the Dan Tian to different parts of the body.
Read on THE MAGUS OF JAVA by Kosta Danaos...
Anyway, I hope that this would suffice and whet your "tongue" on palate practice curiousity.