also, is it typical to hear both a natural extension and the augmented extension of the same note in the same voicing (like how this chord contains both the 11 and the #11)? thanks
at some point i think there is a sort of matrix that falls away and you realize that the way you are using the word 'extension' really means nothing. it may be an extension in terms of which year you may learn it in school. but in the real world i can't think of any reason to say which note of a chord should be considered an 'extension.' i think it will throw you way off to think of it that way. but as far as using E and F in the same chord, try it and see. the chord you gave seems weird but in context it could be fine. don't forget to play it in the song and not out of the song