Yep those engines are ingenious. [8D] Beside some small electrics I own I will buy only RCVs in the future.
Concerning vibrations, have a look at the gassers. There are some models in my Club with gas engines - the whole tail gets blurred when they start hammering.

For my next project I consider to rotate the engine by 45 or 90°, as you did, and to make a hatch as access for the adapter. So its good to know it works without slipping off with the starter.

Cheers
Andi