string numbers (fingering instructions) as roman numerals?

[philip]

Hi,
I was wondering if anyone knows how to override the 
default numbering format for string numbers 
(default is circled arabic numbers) and use roman 
numerals instead. 
An example would be something like this:
{ e''\2 } which is an e played on the second 
string. The default shows a circled 2 above the 
staff. I would like to show a roman numeral II 
instead, so there is no confusion between string 
and fingering indications. Since roman numerals for 
strings are a common convention, i am guessing 
there is a setting in lilypond for it that I havent 
found.
What i have learned so far is that the StringNumber 
is written by the New fingering engraver and has 
both a stencil and text property,  but i have not 
been able to figure out how to change them to roman 
numerals. 
Any help is appreciated.

Thanks,
Philip