the 2005 does allow you to go above .5, you yous the different increments on the side of the tester then multiply by 2 or 5 depending on which scale you use. I know the dpd method is easier. I have been in the water business for over 25 years but when I retired I lost my access to the DPD packs. I have to say pool water is much harder to deal with than city water..pool is very clear so do i need to keep cl level above 10ppm? do i need to take the tablets out, I have no issue putting them to use elseware. How long do I need to keep at shock level? Thanks