You raise a hard problem, there, oohah -- namely, the desire for independent and empirical evidence for a phenomenon that seems to be the essence of subjectivity itself -- the spatial definition of Being. Additionally, it is possible that you are asking to put material processes to work on immaterial phenomena, which is doubly difficult.

But ya know, Bill D has a perfectly workable "friendly skeptic" approach. He speaks for himself and doesn't say anything ad hominem against others, and is respected by all, since he is perfectly friendly. There is no need for skepticism to be upsetting to others, unless you wish to enforce it as the only reasonable path..

A