[NTG-context] Simplefonts: Font scaling problem

Good evening! I want to scale a font loaded via the simplefonts so sans and serif have the same x-height. But as soon as I use a font size larger than 12pt, the scaling is somehow off or ignored. Example: \usemodule[simplefonts] \setupsimplefonts[expansion=quality, protrusion=quality] \setmainfont[Times New Roman] \setsansfont[Arial][scale=0.863] \starttext \setupbodyfont[6pt] 06pt serif xx{\ss xx sans}\\ %fine \setupbodyfont[12pt] 12pt serif xx{\ss xx sans}\\ %fine, too \setupbodyfont[14pt] 14pt serif xx{\ss xx sans}\\ %here it starts to be off \setupbodyfont[16pt] 16pt serif xx{\ss xx sans}\\ \stoptext What is up with that?