Is it correct that the PA-28-161 (and Maybe other Cherokees) won't return to S&L hands off, whereas the 172R (and maybe other 172's) do? In other words, trim out for best S&L and let go of the controls. Warrior slowly but surely dives off one side or the other with increasing bank. 172 returns to S&L as defined by the trim, even if preturbed from level flight.
At least, this is what happens in the two aircraft that I'm familiar with. Engineers shrug and say, "Yes, that's what it does" about the Warrior. I'm not convinced. Maybe it's a safety feature to keep the pilot awake? In the 172 you could doze until the fuel runs out, but not the Warrior.
Incidentally, I can't see how trimming the flaps is any different from compensating with the ailerons? It will only fly straight on the rudder trim with the ball out by about half a ball. You can get better airspeed by compensating with aileron (requires constant pressure), but that is surely an aileron trim issue, nothing to do with flaps?
Any information gratefully received, since it's an irritating and long term issue.