I have been using DIY 2 part for over a year and have no problems with it. For the calcium portion I bought in a pool supply store dirt cheep - will never use enough, so, if you need some or Monti or Chris, I have plenty. For the Alk portion I bake baking powder which I then mix w/ RO/DI and put into a washed out Dishwash solution container (the ones with the pull tops) for easy use. Have had great success.
I never had to add any Mg++ since I do weekly 10% water changes - my levels have been on the higher normal throughout (I did buy Mg++ solution which I never used).