Does anyone know if there is any evidence (not anecdotal) about whether not not sitting crossed legged causes circulation problems/complications?
Yes, my feet go numb if I sit on the floor or on a cushion so I use a low stool with a cushion on to relieve pressure on the knees. I think a straight back is best but have only ever heard "metaphysical" explanations as to why this should be so (kundalini etc)Being comfortable and being able to hold that posture without movement is the most important thing in my view.with Metta
The importance of the stable base is so that once you get deep into meditation, you don't fall over easily (which can happen when you're so into your meditation that you've forgotten to pay attention to the body).
There is some evidence in the sutras that when meditating in a lying down position, what is meant is lying on one side with the head propped up by one hand, as is seen in many representations of the dying Buddha.