The answer to your second question is in here somewhere: www.ksrevenue.org/pdf/cdlhb.pdf[/url
The weight on the registration is immaterial, actually. You can have just about anything there, but if it's wrong you bear the responsibility not the DOT that issued it. It's the actual weight on the day that counts, on the scales, and in most cases the weight is "vehicle or combination of vehicles" so anything in tow like a car or trailer is added in to the bus weight. Up here anything over 6600 lbs has to stop at weigh scales, not just commercial but any and everything, and yeah the police sometimes camp out there and do random inspections.