One advantage so far over looked is the compression ratio
could be anything we want it to be. Merely machining the pocket
differently. The RX8 rotors are 10:1 and that is a disadvantage when
it comes to turbo charging. There is just not enough material there to make the pockets deeper to lower the compression ratio.
On the other hand we might want to make the compression ratio 11:1 to
one to improve the BSFC when burning 100LL aviation fuel.

Paul Lamar