What's the RO feel?

You know it when you feel it, but that might not be the answer you are looking for. The best way to describe it is this: imagine your tone is a very thin thread. You try to grab this thread with rolled out/puckered lips. This focused feeling is the RO feel.. In normal playing your lips will not be as rolled out or puckered as in RO, but the focused and forward feeling towards the centre stays.
The inward movement of the corners is also an important part of the RO feel. You will discover that to ascend you need the same muscles with which you do the RO.