FWIW, I've had excellent results using Ph 5.2, however, I doubt that your mash ph is at the root of the problem. The two main suspects are over sparging and husk particulates making it into the boil kettle for some reason. I would get a second opinion from another brewer before deciding a course of action. IME, astringency problems are not very common and relatively easy to avoid. My point is that perhaps your buddy is mistaking some other problem for astringency, hence the desire for a second opinion. Also, what is your perception of the beer? You will discover, just like most of us have, that you are your own harshest critic. If you don't think there is anything obviously wrong with your beer, most likely you are right.