Very interesting thread@MartinK!
I know you're a shrewd dude from what I've seen on previous forums. It looks to me that you were dead right when you stated a price range of 7/1 upwards might be the way.
That happens to be my own price preference, so I would say that, wouldn't I?
In fact, about a couple of decades ago, some smart boffin put my results through some sort of test ( chi or archie or something?) and concluded that I should stick to bets with odds 11/1 and over. Doesn't say much for my picking power, I must admit, but each to his own.
All the best!