Mash ph and 5.2?

How important is it to know your PH if you are using 5.2 stabilizer?  My thinking is that before this stuff, or if you don't use this stuff its important to know the profile so you can make the adjustments you need to get the Ph where it needs to be.  However, if you are using the 5.2 stabilizer and you assume your PH isn't horribly out of whack to begin with, do you really need to know the profile?  The stabilizer will get you where you need to be right?

Also, assuming your PH is where it needs to be, say via the stabilizer but you are making a Scotch Ale, would you still want to add things to the mash water to make it resemble more of a scotch water profile?

Thanks

WR

I have been brewing 36 years and find that if you have good drinking water that you will make good beer.  I am an all grain brewer and feel that you should know what your mash PH is so that you can have some idea what is going on.  I use test strips on the mash liquid when cooled and find that my mash is in the acceptable range when brewing lighter beer but still use 5 Star 5.2 when the test shows it is getting out of range.  I don't think it hurts to use it without a test but it is good to know about your mash PH.

I use 5.2 on most of my mash's. Dark beers like Stouts/Porters I don't need to because there is enough fermentable's to bring the PH down. I have found that I only need to use about 1/2 as much as the recommended amount in order to bring the PH into line. I only test the water before the grains are added.
Cheers
Preston

Thanks for the answers.  I guess what I'm really asking though is about getting close to certain styles.  Like a Scotch Ale.  Their water is so different than other brewing cities and I have to think that the resulting beer is the product of that differing water (or at least partially).  So, what is the main thing you need regarding the water if you are trying to make something true to style (Like the scotch ale), a good ph or a good combination of different salts to replicate the water profile of a particular city?

Beersmith has a H2O profiler in it. Compare your water to the profile of the area of the brew you are trying to replicate. Then add Minerals / salts or dilute as needed to get as close as possible to the target profile.
You may be able to get your local water analysis on line. I did.
I keep a small supply of calcium carbonate, calcium chloride, and Epsom salts on hand to adjust the mineral content just in case.

John Palmer has a great section about water and how it relates to Beer. You can find it here.
http://www.howtobrew.com/section3/chapter15.html
PH and water profiles are two separate items altogether. The PH is not as important as the water profile as it relates to the mash. Palmer's explanation is the best I have read.
Cheers
Preston