What I'm saying is that my body & lens, is a good 4kg/8lbs of kit.. so when you're waving around 600mm of length.. 1/200th is impossible to achieve sharp focus, handheld.. That said, I'd rather shoot at 1/500th.. 1/750th.. (for me) and at least get some keepers with minimal prop blur, rather than a mess of blurry out of focus shots.
I don't have herculean arms or hands of a surgeon.. Whilst I have a 100-400, it's pretty useless when shooting small prop planes at a distance, so the 600 gets used the most.
Not true practice you will get a good sharp plane with prop blur with a long lens. I do it all the time. Sure you throw out more than you keep but it is possible with minimal practice.