[NTG-context] The last line

Hi, as far as I know TeX has some internal rules (and penalties) for judging where to hyphenate words or not in order to keep a paragraph not too densed and not too loose. Some rules can be modified by commands like tolerance, spaceskip, emergencystretch et al. Now, I want to have control over the last line. I would like to avoid syllables smaller than (for example) 4 letters being the only element in a paragraphs last line. Like this: xxxx xx xxxxx xxxx xx xxx xxxxxxx xx- xxx. Is there a way to make a kind of global definition for this for the entire document? Thanks for any hints, Steffen