I would say 2-3 capsules a day since one didn't seem to have much effect. I'll see if I can find out how much they used in the trials for myotonic dystrophy.
Since they're 1000 mg maybe start with one and see if you notice any change, and if not go to two.
I checked lots of articles and couldn't find anything on recommended dosage, so I guess you just have to experiment. I would suggest taking it before bed in case it makes your muscles really relaxed at first or lowers your blood pressure.
I'm glad you brought this up again - I only took 500 mg and didn't stick with it very long so maybe if I had increased the dose I would have seen more results. Someone wrote a post a while back about an energy drink that helped her myotonia and it also contained taurine.