rotorspeed
"I find your analysis hard to believe in entirety and it is certainly flawed in principle."
Fine. In the words of the old adage: 'Advice is only worth what you've paid for it'.
"In reality the SFH cost includes pretty much all the indirect costs .............. etc"
You've answered that point in your final sentence.
".............. I would strongly argue that the majority of maintenance is a direct cost of operating the aircraft."
The contribution permitted under the exception is not to the "direct cost of operating the aircraft" but to the direct costs of the particular cost-sharing flight: Article 160(2)(c).
You're free, of course, to argue that what I've described as indirect costs are actually direct costs. My intention was to discourage pilots from putting themselves in a position where they might find themselves having to argue that they did nothing illegal - or worse, having to concede that they did.
I happen to think owner-pilots should be permitted to accept contributions to certain specified indirect costs, but that's not what the exception says.
FL