[NTG-context] letter module, vertical offset of reference line

Hi, I need to adjust the vertical position of the reference line (as well as subject, opening etc.) because the info-block is longer than the addressee-block to the left. With alternative=customized I can use \setupletterstyle [firstpage] [topspace=...] However with alternative a and e setting topspace has no effect. Also \setupletterstyle [reference] [voffset=...] changes the offset for alternative=customized, only. Best, Florian