Thanks for submitting, the request is under consideration.
Note that the charts fill up the space given, to force the size of the KPI limit the height and allow space for numbers if they are dynamic. The Multi KPI in the viz bundle works differently, it has fixed font size that might be useful.
KPI layout options: Fixed (text always the same size), Fluid (text adapts to box size but not text length) and Responsive (text resize to always fit, this is the current default setting). Probably is "Fluid" what you want.