A basic presumption of the NMRA car-weight recommendations is that uniformity of car weights contributes to fewer derailments. The precept applies to all cars, whether there is a modeled load or not. If adding loads to cars creates significant weight differentials, then you're not following the recommendation. The effects can be countered by placing heavier cars at the front of the train (that is, near the locomotive), but I wouldn't think something like a half-ounce variance in HO scale should cause concern.
Mark
Good afternoon folks. I have incorporated the NMRA Weight RP into my collection, but have a quandry that I haven't seen explained anywhere, including the hundreds of posts on car weighting contained in this Forum. The weight recommendations are clear for certain cars, such as box cars, cabeese, tankers and covered hoppers, but what about gondolas, open hoppers, bethgons and flats? If the cars are at spec and you add a load, it becomes too heavy (or at least heavier). This inhibits "loads in / empties out" operations. Am I missing something? I'm sure that this sage forum will set me straight. Thanks in advance for the information.
Len S