If you have a pH meter and are curious about 5.2, do the following.
1. Calibrate your meter.
2. Mash some pilsner malt with some distilled water, stir well, let sit for 10 minutes or so.
3. Test the pH
4. Add the recommended amount of 5.2
5. Test the pH
6. Add more 5.2 up to twice the recommended amount
7. Test the pH
8. Repeat steps 6 and 7 until you are convinced or you have run out of 5.2, whichever occurs first.