https://www.championpowerequipment.com/product/100319-50-amp-parallel-kit/I saw somewhere this is also good with the Predator 3500s so that makes sense.
I saw also there is a "Powerhorse" similar to a Predator, and its NT parallel kit has a 50 but needs an adapter for an RV 50.
https://www.northerntool.com/shop/tools/product_200660537_200660537Not clear on VA out when paralleled. Bogus sales talk of "double"
the power etc.
Some confusion over what the "3500" means. It is 3000w continuous