I purchased a flashflo about a month ago. I have been a runner who always stashed water around the subdivision but lost my hiding place when the developer completed the buildout. I tried a bottle type waist carrier but was bothered by the sloshing/bouncing. Threw it out after one run. I bought the flashflo after careful concideration. I was really looking for the Bandido, but that model was discontinued.
The unit has excellent adjustability for the belt. The pack is shaped so it rides just above the butt and is not really noticable. It also has side straps that cinch across the bladder preventing the bladder from moving during the run. Because the bladder is air-tight, no air is in the bladder and as a result, no sloshing. I have enjoyed the unit in the 3 long runs to date.