Val there is no good research on flipped classrooms that I'm aware of. That doesn't mean research isn't underway; I'm sure it is. However, research take time to develop (acquiring funding, conducting the research, interpreting the results, the peer review and publication process, the public vetting of studies once they appear in print). The process takes much longer, unfortunately, than fads take to spread across classrooms.
I agree with 22B. A mixed approach is by far the best, albeit this is anecdotal evidence based on my own experiences as a teacher of writing, literature, and women's studies and as a parent whose child's school has double periods of math and language arts where formal instruction (lecture) and workshop (independent and group work with peer and teacher support) are a part of every class session.
