If you really want to help the tractor handle the lifting better fill the loader bucket with a scoop of gravel. I do this when I pull loaded corn wagons with my JD 6300 MFWD. It makes a world of difference. Even a small bucket of gravel would be more than the cast weights you have coming. Plus it is way out in front to help counter balance the plow better.
Also does that smaller Kubota have draft control??? Many of the compact tractors do not have any draft control. That makes plowing with them harder.