Hi Mick
The difference is you trend your engines. Jo blow average doesn't and that's a big difference. I at the end of the day see burnt valves by people experimenting with it. Then they cry at the cost. The fuel saved will never make up for the cost of the repairs. As I recall Cessna allows it in there POH. I don't think by memory Beech do I will stand corrected on this.
A classic example of trending is the RFDS they get 8000 o/h out of a PT6 due trending when the o.h limit set by Pw is 3600. Things are fixed before they become problems.
Like I said earlier, you should be commended on your approach to your business, I just wish there where more operators like you it would make my life easier. I am open for ideas. Bit hard to do any courses for me I am in the middle of no where.