removing naturals

[Peter Buhr]

The following is a left-hand octave-exercise for guitar. It has no tempo.  I do
not want the natural symbols to appear in the exercise. I used
"Staff.extraNatural = ##f" is an attempt to eliminate the naturals as per the
instructions on page 6 of the Notation Reference manual, but that did not
help. Is there a way to remove all the natural symbols?

Also, is there a way to increase the font size of the "8" in the "treble_8"
clef?

===============================================================================

\version "2.13.3"
\include "english.ly"
#(ly:set-option 'point-and-click #f)
#(set-default-paper-size "letter")
#(set-global-staff-size 23)

\paper{
    tagline = ""
} % paper

\layout {
    indent = 0.0
    \context {
        \Staff
        \remove "Time_signature_engraver"
    }
} % layout

\score {
    \relative c {
        \set Staff.extraNatural = ##f
        \clef "treble_8"
        \set fingeringOrientations = #'(left left left left)
        \cadenzaOn
        <e,-0 e'-2> <f-1 f'-3> <fs-2 fs'-4> <g-3 g'-0> <gs-4 gs'-1> <a-0 a'-2> 
<as-1 as'-3> <b-2 b'-4>
        \stemDown <c-3 c'-1> <cs-4 cs'-2> <d-0 d'-3> <ds-1 ds'-4> <e-2 e'-0> 
<f-3 f'-1> <fs-4 fs'-2> <g-0 g'-3> <gs-1 gs'-4> \bar "|"
        <g-0 g'-3> <fs-4 fs'-2> <f-3 f'-1> <e-2 e'-0> <ds-1 ds'-4> <d-0 d'-3> 
<cs-4 cs'-2> <c-3 c'-1>
        <b-2 b'-4> \stemUp <as-1 as'-3> <a-0 a'-2> <gs-4 gs'-1> <g-3 g'-0> 
<fs-2 fs'-4> <f-1 f'-3> <e-0 e'-2> s4 \bar "|"
    } % relative
} % score