We have a stone stomper for the van also and it works great.
Tool boxes 34 kg, frame 6 kg.
We will take it to Jayco and get a confirmed ball weight amount from previous to now. I don't think the weight is proportionate. IE add 40kg on drawbar at rear, might only add 20 kg to ball weight? That is not fact by the way, just a guess as weight is not right on the end of the draw bar? Happy to be informed though.
My biggest issue was carrying the weber in the small door and taking out, that was one of the main reasons for getting the boxes. The second big reason was for extra storage, the front storage was a nightmare for me being disorganised!!!! Sullage hoses, power cables, kids chairs and table, water hoses, all light but bulky will go in the front boxes now.