4-Drum Conga Notation in LilyPond

[Eric Pancer]

While writing some conga exercises (for four drums) in Lilypond, I've
found I can get by using the following notes*:
 - bd (super tumba)
 - toml (tumba)
 - sn (conga)

However, I'm looking for a 4th pitch to notate a quinto (high drum)
and would like to use E6 (4th space in treble clef). Since there's no
standard notehead for that in
<http://lilypond.org/doc/v2.12/Documentation/user/lilypond/Percussion-notes>,
could someone please advise on how to change my file to redefine the
pitch with the correct notehead?

Also, is there an easy way to make each pitch with an "x" (slap)?

Thanks,

- Eric

* - I realize that LilyPond does have a built-in way to notate congas,
but I'm already working with a system that notates 4 drums in a
standard staff.