Changing Angles is an interesting site concerned with analyzing various aspects of skating. Regarding the geometry of skateboard trucks the author is very thorough. What I didn’t find yet is where he discusses horizontal bushing compression, which appears to be part of the feel of a truck – hence “wrong” pivot axle/cup angles and large kingpin holes in the hangers as a design landmark for decades. Trying to force this design into a non-slop one will eventually destroy the pivot and cup, as he already documented himself (see figure about spherical bearings).