I think you're under estimating how hard it is to actually get a proper seal with a piece of tape. The valved n95s I've seen are a bit fuzzy. You can certainly

I think you're under estimating how hard it is to actually get a proper seal with a piece of tape. The valved n95s I've seen are a bit fuzzy. You can certainly block most airflow, but there's still a small path at the intersection of the tape and mask that can't be properly sealed. For the layperson, that's fine. For a scientific study, that's a problem.