Anon,

here is my 2 cents based on my experience with my daughter’ treatment.

first, I agree that every child is different and the dosage should be based on the blood test result.

second, I think you should watch for the trend of his blood test result and keep in mind that babies are growing very fast. Look back at his blood test results, is it going up (even they are still within the normal range) ? babies grow very fast at this age, it takes short time for them to outgrow the dosage they are on. 

My daughter’s endo cut her dosage to 2.5mg a day when she was around 4 months old based on the blood test result.  I always feel that was a very low dosage. We had another test when she was 6months old,  her 17OHP was up but still within the normal range.  We tested again when she was 8 months old, her 17OHP jumped to 12K. Now she is on 6.25mg per day and her 17OHP is still above normal (1700). 

I think if your son is on a low dose,  you should have him checked more frequently.

Good luck.