From what i remember reading on it theres something in raw soybeans that is counterproductive to growth so they needed to be roasted first. Seems to be plenty of articles about it on the Google.
I came to the conclusion it was better to sell the beans and buy back feed but a have been wrong before.
I know the neighbor said they tried it years back and didnt have much luck fwiw. They just ran em thru the hammermill along with ear corn i assume
Your decreased weight gain comes from the bean being 40% oil, which means more fat less meat. In conjunction with another protein source, and reduced corn in the ration, it is perfectly fine. Plus you get a boat load of natural estrogen.
When used properly the only con is it's price. High beans, and low corn, your better off just feeding more corn and using other proteins.