Put scalenodeweight and scalebeamstuff in the main jbeam file. Check hatch.jbeam for how it should look.
Could someone make a mod like 2000kg box please i don't think it's too hard for modders. For modders it's probably tier 0 modding.
For most people its tier 0 modding. Open the Jbeam. Find the nodeweight parameter, increase/decrease it as you see fit.