jabiru aren't unique in experiencing engine problems.
crankcase through bolts used to fail on VW conversions.
the cause was too heavy a prop bringing the harmonic vibration speeds down into the operating rpm range.
overheating heads were experienced by one of the european motorcycle manufacturers.
the solution was to move the transition to the exhaust pipe closer in to the valve seat. this took heat from the head and pushed it into the pipe which could be cooled more easily and wasn't as temperature critical.
the core challenge in fixing problems is to identify the actual cause.
sometimes it needs the calling in of some smart boffinry. (that's a hint jabiru.)