How to adjust text options for subtitles in a simple twoway plot using -by- ?

Code:
sysuse auto, clear
tw scatter mpg disp, by(foreign, title("Not here", size(4)))
tw scatter mpg disp, by(foreign, subtitle("Or here", size(4)))
Various options using title/subtitle/subtitle1/subtitle2 in the -by- and outside....have failed. Surely it's right there!