quick,
Good choice
You have to use your past as your new guidance:
You've gained with IPR.
You have gained with everything else.
Not saying that you should drop all and switch back to IPR. You also didn't gain with IPR the second time (it appears your penis adapted). . . but one thing is clear: your penis grows with rest!
My advice: keep switching it up (every two weeks or so) and measure often. Find out what works best for you.