I use PH 5.2 stabalizer on beers that have mostly base malt as the grist. I'm not sure I need it though, and probably wont buy it again. I've done the same beers without using it and haven't had conversion issues, or change in efficiency.
When I brew light pilsners or the like, I use mostly RO water and build up the water from there. The PH from my RO system starts at a lower acidity than tap water, so If your using tap water on a light beer, PH 5.2 would get you to the proper ph in your mash, with our alkaline tap water.
Not thinking it's needed though,