The Thielert 4 stroke 4 cylinder engine or any 4 stroke engine deisel is not a good design to drive a prop. To many harmonics and large power pulses.
That is why it needs a gear box and harmonic damper. Does not follow the KIS concept, Keep It Simple.
The SMA needs a very tough prop that can take it.
Externaly blown 2 strokes are far better, I think you need to wait for the Delta Hawk V4 160/180/200 hp or the Wilksch 4 cl 160hp no FADEC in either.
Far better design concepts.
The 8 cyl twin row 2 stroke radial Zoche would be the best and smoothest but it seems to be a scam to get EU grants and will never see the light of day, been in development for at least 20 years.
I would steer clear of Diamonds own, to heavy and all the problems of the Thielert.
I agree about Lycoming IO360 or O360, lots of valve and cam problems due
to poor oil flow to the valve gear and oil draining off the cam and rusting, if not flown regulary. 40 hours a month, so Lycoming say.