Thank you so much, Shawn,
Interestingly I just had a beautiful practice before reading your message, and what I tried was exactly what you said. I invited my tongue to be in that position at the beginning and then let it go to do what it needed to do. You were right that sometimes it drifted back to the roof of my mouth, while at other times it did other things. Most importantly, it didn't distract me too much and I was able to feel the energy and have a really enjoyable session, both with some active exercises and the small universe meditation.
Thank you also for the clarification of exactly where to put the tongue. I had wondered about this, at the place you mention is certainly easier (less tension) than trying to put the tongue any further back.
Lastly, I am trying to do my practice around solar noon when possible, since I believe Master Lin said that the front and back channels connect automatically at this time. (And at midnight, but I would fall asleep then!) I appreciate what you said about having the intention that the channels will connect no matter what my tongue does - I was hoping that would be the case!
It is wonderful that your advice and my intuition converged! Thank you so much! I am grateful to be back to practicing (and to have it be a positive experience again.)
All the best to you!