I tongued for forty years with the tip of the tongue between the lips because a Jr. High school teacher taught me. To make matters worse by the time I got to a pro trumpet teacher who learned from Gordon, sadly he didn't pick up on this. We were too busy fixing all the other incorrect playing techniques I had learned. On to the point.... Almost every good to excellent player here on TM will tell you to put the tip of your tongue behind your lower teeth, either floating or locked (not as popular), and articulate with the forward part of your tongue on the forward part of your hard palate. I was skeptical at first but have made the change and it came very easily. Two items behind this rationale: 1) tonguing between the lips can easily 'push' or 'move' the lip set with each attack, do this long enough and you won't notice it but that does not mean it isn't happening. 2) This minimizes the tongue movement when articulating. Generally the less movement of the tongue the better. More so - with this technique double tonguing is also faster with minimal movement and provides minimal interruption of the overall tongue setup. With a bit of work 2x tonguing becomes a rocking motion and goes much faster, again... minimal motion. BTW this was one of the 'learned every bad habit a trumpet player can have from a band director' rant. I've spent a lifetime relearning the basics of good playing. What a PITA! PM me for the whole list of things not to do.