When the tongue is placed towards the front right behind the teeth there is a noticable energy circuit redirecting energy flow towards the third eye. I tried some thing new the other day and placed my tongue toward the back/roof of my mouth and I felt a noticable current go toward my crown. I could even feel/taste the sensation in my tongue. Try it out see if it works for you. I pretty much just breathed energy into my crown while holding my tongue there, but I definitely felt it and have read about this no where.

https://www.ancient-forums.com/viewtopic.php?f=17&t=17061&p=64530#p64530

Yes, this is even done in Falun Gong. It creates an energy connection from your lower chakras to your chakras in your head/above.
HP Lucius had written to me about it before on a Falun Gong thread we had on the older forum that explained its history and application.
I dont have the link to it before (probably gone from the archives anyway), so hopefully he has the time to come here and perhaps re-iterate it