As far as a target concentration to shoot for, Jim Humble claims to have had 100% success in Africa using a concentration of 1 PPM free chlorine dioxide. I think that is a good target to shoot for.
Activated sodium chlorite solutions have been used for years. Much testing has been done to determine optimum activation. If you activate with 10% citric acid in a 1:1 ratio and let the activation continue for 10 minutes, you end up with a solution that has over 30% more disinfecting power [edit: Oops I looked back through my test data and this should be 40% [end edit] than a solution made up following the Miracle-Mineral-Supplement protocol.
[edit] This should read 40% [end edit] 40% stronger means that you can take 40% less and have the same effect...