Hi, I used an appropriately sized ring spanner that I had (about 15mm). I could see what was happening with my lips.

Didn’t use it that much in the end but I could see what was happening and more importantly what was wrong. Then just used the mental picture when playing a proper mouthpiece and have that voice in my head that says don’t force it, particularly higher up the range.

Not sure whether its the right thing to use but I found it helpful. I think after initially doubting the concept of the visualiser the concept is actually very good.

Mike