the edge of the rim is sometimes a bit damaged so that the radial dial takes the tire bead surface with this truing stand.
last time i worked on a wheel i had the inner surface of the rim (next to the eyelet, tire mounted) measured - optics involved with a laser tool.
as for lateral runout... i don't care for exact measurements. i just minimize it as best as i can (<0.1mm) using just a zip tie.