[NTG-context] Superios with Cardo font

[Denis Maier]

Hi,

I am trying to use the Cardo font with superior figures. But somehow 
these seems to work differently here than with other fonts:

====================
\definefontfeature[default][default][
     onum=yes,
     pnum=yes,
     ]

\definefontfeature[f:newstyle][onum=no,pnum=no]

\definefontfamily[cardo][rm][Cardo]
\definefontfamily[libertine][rm][Linux Libertine O]

\starttext
\setupbodyfont[cardo]
12345
{\feature[+][f:superiors]12345}

12345
{\feature[+][f:newstyle]\feature[+][f:superiors]12345}

\setupbodyfont[libertine]
12345
{\feature[+][f:superiors]12345}

12345
{\feature[+][f:newstyle]\feature[+][f:superiors]12345}
\stoptext
====================

Why is it that I have to manually disable onum and pnum with Cardo for 
sups to work?

(Note: Cardo is a ttf font, Linux Libertine O is a otf)

By the way, what is the correct way to define a new font feature for 
superios? (VerticalPosition=Superior; sups=yes; 
VerticalPosition=Superscript ...)

Best,
Denis