Rod Stiff has been warned many times by highly qualified engineers of the problems with the engine that are easily identified by known mathematical theory such resonance issues within the engine.
Oracle 1
Could you shed some more light on the resonance issues. I havn't had any hands on experience with Jabiru engines but I have 'heard' that resonance can be a problem if any prop other than a wooden one is used and that Jabiru only approves wooden props.
I 'heard' that the flexible nature of a wooden prop acts as a quill shaft or as a torsional balance . If you use a fairly inflexible composite or worse a metal prop things will break inside the engine. I'm sure you would have knowledge pertaining to this and will be able to clarify the situation.