In further reading these posts I'm reminded of the C-47 I once had something to do with.
When doing the run-up one of the pilots in particular would do a 'free and correct' with power on, the resultant movement of the fuselage was very evident - and presumably obvious from the cockpit had something been wrong.
I never tried it myself, so can't report on the control forces etc, however for a craft where you can't see what's happening behind you I guess it had some applicability. For me I was a little reluctant, thinking of possible damage to control surfaces from stones etc, particularly as we did fly it a lot from grass strips and those big props on full noise sure kicked up a lot of cr*p.
FP.