It has been a bit since your post, but I recently moved into Stonegate. I have been using a mineral mix that is sold in bulk quantities that will adjust your mash PH to 5.2. I have not had any problems yet and beers have tasted good.
My only concern might be the sparge water that I have not treated, but so far, it has not caused any problems, even with lighter ales. I always figure a little gypsum never hurts either...
Hope that helps!