for performance it is better to have parallel squish (and no radius at the edge of the bowl, Jan Thiel has tested this extensivly at Aprilia) . I only put tangent as a possibility as that is what some people want.
17° surely is a lot

from memory mine are amways arroung 10°
but it all depends on the correct radius offcourse.
You know it's cold outside when you trip over dog shit instead of standing in it.