Psionicist said:Thongs are popular and mainstream now so I guess they are at least moderately comfortable.
Popularity has virtually nothing to do with comfort. Polyester isn't a comfortable fabric, but people wore it en masse in the 1970s. Some people blame that on the.. recreational pharmaceuticals.
Or, look back at Victorian Era women's fashions. Ye gods, that couldn't have been comfortable. Any clothing that enduces swooning isn't comfortable.
Now, in a vain effort to steer this back to the supposed "science", I suggest folks go and read, "A Stress Analysis of a Strapless Evening Gown" by Charles E Siem. The essay is available online, and the book (ed by Robert Baker) is available at Amazon. No link because some folks might not feel the structural diagrams are work-safe.