Head down- IJ falls out of Zone I and greatly increases flow, unlike in microgravity. Also, the release of the thoracic viscera from the gravitational load will not be represented adequately in 1-G.
Parabolic studies will show some acute changes but may over or under represent the findings. Also, it is the longer-term changes that are most important.
An open access to data for study of the findings of individuals in microgravity will lead to more eyes and brains on the subject and more and faster results of study.
In microgravity, the ideal study method for Zones II- IV is transesophageal ultrasound because external ultrasound will be blocked by ribs, clavicle, sternum, etc.
Invasive venous pressure studies would be useful. As would doppler flow studies of symptomatic and asymptomatic individuals.