Right, that is why to be safe we did register for 46,000lbs. However, certain states automatically registered our truck for higher amounts because it is listed as a 3 axle vehicle. According to DOT this is their option, just as each state seems to make up it's own rules regarding the use of them. Plus, we were informed that the type of pusher/tag you have is considered by the DOT. For example, some have one wheel per side, some do not have brakes, etc. The DMV told me here (VA) that our truck would come with the weight that it could carrry on the orignial registration, ours said 54,000lbs.
You are also correct that you can register your vehicle for higher amounts. As a matter of fact, we have just heard of some perople possibly registering their truck for 55,000 lbs to avoid the sales tax in their state but then paying heavy highway usage tax...which is only about $100 per year in their state.
BTW, Sharp, we surely have gotten lucky lately as far as LA goes. We have been through there 4 times since your post regarding the fine you received. Once with pusher down and now three times without. We were wieghed 3 times and got the bypass sign once.
ALSO, just out of curiousity why is LA the only state we can think of that requires you to BYPASS scales when the sign is flashing? This was very confusing to us when we first started driving.