Sorry to hear about Jo's discomfort. I wouldn't chance giving him the hurls or runs, just to try a higher dose than he's accustomed to.
MMS doesn't seem to knock out flu/cold symptoms better if you strengthen the dose. More frequent doses of a smaller size might be of benefit. (Although you might want to try topical ear drops and nose spray, plus gargling in the throat and roof of the mouth before swallowing.)
If you have DMSO, you might add a few drops of that to his regular dose, but if he's at his upper drop limit, try lowering the drops before you add DMSO. I tried 20 drops Miracle-Mineral-Supplement with 10 drops DMSO one time, and let me tell you, the next 24 hours made me wonder why we're using "ethanol" as an alternative fuel. :)