this is completely off topic, but its to do with incidents post, ok, i thought something like F8 could exsist? Let's looks at the Cmaj

C D E F G A B c d e f g a b c.
1i 2 3i 4 5i 6 7i 8 9i 10 11i 12 13i 14 15i.

the i are all the notes i would use if i continued the c maj voicing. I would actually use 1,3,5,7,9(which is also 2nd, but it's an octave up), 11(same as 4th, but again an octave above), 13th(same again), 15th.
Now, is this how you get 11th chords for example? and why can you simply not add a second?
And could you not have power chord with an 8th instead of a first? (I know this in not what was meant).
thanx