In the attached file, loading the font with \setupbodyfont gives
narrower interline spacing than with font (you have to comment out the
\setupbodyfont line to see this), I'm not sure if this is normal, but
the first case gives different interline spaces from line to line. I
tested it with two different fonts.

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer