I think that would be a good idea. Either your body isn't used to it yet or 30mg might be too much. The 10mg later in the day should really lessen the irritable drop off in the afternoon.
both of those symptoms are characteristic of the meds constricting the small blood vessels as it drops out of your system. My solution? I drink a hot coffee in the early afternoon which tends to dilate the blood vessels and will keep them like that while the meds drift off.
The cramps I get - the headaches I don't. I drink lots of coffee most days though so that is probably why. I have Irritable bowel - which is sometimes aggravated by my meds. According to my doc it's because of the med's known tendency to rythmicly constrict smooth muscles in the body which include blood vessels and the intestines. Most times it's because I missed a meal and it's air in your intestines being banged around back and forth. My MD prescribed me dicetel which is very mild and relaxes my system great!