Bonjour,
The M30, also very nice machine to my opinion, has a great advantage compared to the M31, it has no dead points:
Operates at a few PSI.
My lonely small concern would be the size of the flywheel, quite large to be installed in a hull.
And if you know French steam designers, André LECOMTE created his famous AL5 a few decades ago:
A little family resemblance?