My coal hoppers weigh 4oz like they should according to NMRA standards. I want to increase the weight to try to fix some minor derailments. I want to add 2oz of weight. I will be pulling twelve of these cars with a Proto 2000 dc GP38-2. At what point is enough enough and too much stress on the engine? Thoughts? I have my track laid and I am ready for either ballast or to start laying chicken wire and paper mache' the land forms. I need some thoughts on which order to do this. I know it should be ballast, but I almost want to do the landform first. Thanks for the helps.