I am a PhD student in Spain and I plan to spend 6 months in the US to work on a research project (non-degree seeking student, not paid by the hosting institution, research stay not required by my institution, but will be "officially set [you] up as a Research Assistant working for me by just filling out a form").
I am awaiting information from HR of the hosting institution but in the meantime I am checking the various requirements. I just read that for the J-1 (short stay), institutional, governmental, business, or agency funding must cover at least 50% of the minimum funding required. I am not sure I'll be asked to apply for the J-1, but this would prevent me from coming there since the available scholarships would cover less than 50%. Is the J-1 the right visa type?