Hello Thierry
I am sure yoy now have the solution. I have exactly the same "problem": Cessna 2.10 m and the OS 160 Twin boxer. I only need to move the engine around 6.5 cm and plyvood
is the perfect solution . Maybe you have ansver on the next problem....how can I/we move exhaust on my Cessna 182 to exit the cowling in a scale location ?
Good luck with your plane
Flemming