NASA thought rotaries could be useful in light aircraft in the 1980s.
Not exactly light reading, but their Technical Report server has some publicly available papers.

I thought this summary of experiments from 1984 was interesting.
In addition to Curtiss-Wright engines, they modified a 12A to a single rotor and turbocharged a 13B.
Rotor and apex seal coatings were also tested, but so far I haven't seen a follow up paper with the results. I'm guessing they weren't great.