capital letters for right hand fingering?

[Blöchl Bernhard]

How to get capital letters for right hand fingering? I add an example 
code.

#(define RH rightHandFinger)
\new Staff \relative c' {
   \set strokeFingerOrientations = #'( down)
  c-\RH #1 e-\RH #2 g-\RH #3 c-\RH #4
}