I also was pondering a similar experiment with my Octoberfest/Vienna Lagers, and I have been looking for any data on what the fnishing PH of beers tend to be. I have not found any data on what the PH of finished beer tends to be, or if it varies by style, or over time as the beer ages. I percieve a change in malt character as it ages, and I percieve I have noticed this even in the comercial examples I keep on hand. The PH papers I have on hand that go down to the 3 range, show a change in PH as well, however, since they do not have the significant color variation of the ColorPHast strips I use for the higher PH range, it is hard to get very exact... other than to say the PH dropped a bit as the beers aged.
Some thougths I had for the experiment was to add a base as well as acid to provide a wider range of data values. I also have been trying to decide on the best acid to use... citric, lactic, phosphoric...other... each can have a flavor contribution if the levels get high enough, and that may cloud the results a bit.
What got me started down this line was my fist batch of cider I brewed a year ago... It was OK, but kind of "flat" tasting. One day, while brewing, I had a bottle of cider in hand during the mash, and I decded to add some acid to it... just a drop of citric acid I had on hand... and it was a completely different set of flavors that I tasted. As I read more, I found the PH in food is often sited as key factor in flavor perceptions. However, I could not find any data on finishing PH and beer.