[NTG-context] Learning about Kerning

Hi, I am trying to use kerning in subject titles. \kernchracters works pretty good, but as you can see in the attached example, there is a gap before the Ts in Properties, and again in Praefatio and Praefationis. The \stretched command yields similar results, vis-à-vis the gaps. If somebody can enlighten me how to properly use kerning in this situation, I'd be immeasurably grateful. Cheers, Michael