full rich all the time, that's a dangerous practice - What?!
That's what I said. Book endurance figures only work if the engine is leaned for cruise in accordance with whatever assumptions were made by the book writers about cruise engine settings.
Ironically in this case, the actual hourly fuel consumption was probably
higher than the (very rich-for-cruise) 75 litres per hour assumed for planning. By my count, there were 5 take offs and a number of very short legs. During all of those take-offs and climbs I'm assuming it was 'balls to the wall', in which case the engine was gobbling in the order of 100 litres per hour (unless the pilot was using the target EGT leaning during climb technique, but even then the fuel consumption would have been much higher than 75 litres per hour during take off and climb.
For example, I'm pretty confident that during the 30 minute flight from Katalpa to Pine View Station the aircraft consumed more (a lot more) than 37.5 litres.
Fuel consumption for a 4.5 hour trip with one take off and landing is vastly different than a 4.5 hour trip with 5 take-offs and landings (including manoeuvring in the circuit and taxiing at each).